Roy Mustang

Roy Mustang Is an alchemy-based spell caster that uses flames to burst his enemies. He isn't very durable, so he's mainly used as a backline high-DPS dealer who use's alchemy-infused autoattacks when his spells are on cooldown.

Abilities:
Passive F, Flame Alchemy: Due to the nature and power of Roy's Flame Alchemy, he will deal 30% damage to any target near his initial target on each hit.

Q, Combustion: Mustang snaps his fingers and causes a large explosion in the target area, dealing damage and stunning enemies there. 300 Aoe, 900 cast range, 25 second cooldown. 300/350/400/450/500 damage, 0.50.630.75/0.88/1 second stun.

W, Inferno: Mustang transmutes an explosion of fire at the target point, which bursts open in a radius of 250 and deals damage and knockback away from where it was thrown. 350/400/450/500/550 damage. 1200 cast range, 25 second cooldown.
 * This ability's damage is increased by Roy's alchemy if Flame Alchemy gloves are bought.

E, Eruption: Mustang transmutes a bolt of fire which will fly through the air and land on the target area. The bolt then explodes launching another 144 tiny projectiles off which land in a huge ring and radiate outward into a very large AoE. Most damage is done at the center 150 Aoe. 800 cast range. 30 second cooldown. 0.25x/0.4x/0.55 Mustangs Alchemy bonus damage in the center and 250/400/500 damage in the outer ring. [*]This ability has a minimum cast range. If cast too close to Roy, the game will arbitrarily cast it out further from him.

R, Incinerate: Mustang transmutes a constant spray of flame that rotates around a target point for 7 seconds. Those hit by the attack will take 21 damage per second for 5 seconds afterwards, 700 AoE, 800 cast range, 60 second cooldown. 60/65/70/75/80 damage per fire blast.

Upgrades:
Flame Alchemy Gloves: These gloves will strengthen Roy's W by making him deal his Alchemy stat as bonus damage, and buff's his Alchemy by 30. It does not matter who buys the item, Roy will get the effects if he is in the game. Can only be bought once.

Playing as Roy Mustang
Roy is the most direct squishy mage of Alchemist, having high damage and range but low durability. He must keep his distance to stay alive and get out all of his damage. His primary tools for not dying are his Q stun and W knockback, and his W is by far his most important spell in general, and its use will largely determine how skilled the Roy player is. E and R do not provide any effects other than damage, and quite frankly his E doesn't even do that much damage in the first place. If you have lost levels, make sure to always re-level your E last, given it is by far your worst ability.

The most important thing that not everybody knows about Roy is that his R does by far the most damage in the center. The ability is a bunch of dummy Breath of Fires being cast, and being on top of where the abilities are cast gets you hit by all of them regardless of how the animation appears. Because of this, Roy does massive damage to NPCs because they will sit in his R for the entire time if centered on them properly. A bad Roy will generically spam all of his spells onto a single point immediately, and this is far from optimal. The knockback of W will knock the target out of the R, preventing most of the damage. In addition, Roy's E does the least damage in the center as it explodes outwards, so you want to aim it to the side of your target.

For maximum damage to an unmoving target, cast W first, so that the knockback does not interfere with R. Cast E simultaneously so that the target is knocked through all of the waves of E. Only once the knockback from W has stopped, cast R directly on top of the target. Q can be cast at any time, its timing does not have to be so specific for max damage. Of course, you are not going to have the luxury of attacking an unmoving target most of the time with no interference. If a bunch of homunculi are guarding doctor, just cast Q E R on the doctor and don't cast W at all to avoid preventing damage of R. Because of how quickly Roy dies, getting out your R onto the doctor in a sewer fight is by far your most important job.

In addition to interrupting your own R with your W knockback, another key channel skill that is important to avoid interrupting is Alphonse's R. Alphonse's R is even more damaging than Roy's R, but most Roy players will carelessly knock targets out of the way without caring, rarely letting it be utilized. Ed's E walls will prevent you from knocking back a target, which can often be a good thing to prevent you from messing up another combo. Feel free to just throw out your W for damage in such a scenario if stun is no longer an issue in the current fight, though you may want to save it for after the cage wears off if you think the victim can escape.

While Q is a very casual stun, W is what makes Roy so powerful when aimed properly. Being able to send homunculi away who would kill you or a relevant ally, in addition to knocking them towards you to prevent them from escaping the team, is incredibly important. Messing it up and knocking homunculi in the opposite direction as intended can be devastating to a game, to the point it can even outright decide a win or loss for the team in extreme scenarios. To aim properly, try to stun with Q first if you can. While this will not guarantee the knockback goes through, it can help to ease prediction against the target homunculus. Overshooting to the point you miss can also be preferable to knocking a homunculus in the wrong direction, don't cut it close.

Roy's R has a 60 second cooldown compared to the much shorter cooldown on the rest of his abilities. From a fresh fight, it's rarely worth it to do the proper W + E combo to get maximum damage out of E, given it's far worse than just placing R in an optimal place. However, if a fight is ongoing and your Q/W/E have come off cooldown while your R is still unavailable, this is the time to finally try to make use of the combo. Save E until your W is used if you can, given if you just mindlessly throw it out it barely does any damage anyway.

At the start of the game, Roy is able to kill roughly 600 bears in the bear cave before 36 minutes to attain level 35, while getting tons of gold in the process. Roy's early game presence is very useful, but if nobody else is using the cave, getting most of the money needed for your book early game is too much of a good deal to turn down. Other characters kill the bears more slowly by comparison, and Roy enjoys the book more than most to take his damage to the next level. If other worse grinders need the cave, though, do not hesitate to give it to them, as it's not like a Marcoh is going to do much early and can still get most of the gold.

The gloves upgrade is generally not worth the money, especially if you don't have a book yet. Keep in mind you are trading 2 false stones and 40 gold in exchange for 20 intelligence and 150 extra damage or so on W. While it is nice, W is primarily a utility spell, not for raw damage, regardless, and the extra intelligence is irrelevant given Roy will never run out of mana in the end game.

Roy Mustang Vs Sloth
This gets a special section given these two characters have pretty consistently been the two most meta defining characters in the game, and there is a lot of interaction between them.

Sloth's R is very casually interrupted by Roy, moreso than any other character, which makes him one of the closest things to a counter Sloth has. Both Roy's Q and W interrupt his R instantly for whatever reason. When Roy has not one, but two spells that instantly interrupt Sloth's R, Sloth will probably want to save his R until after Roy is just dead already if possible. Roy's W is already an extremely important spell in his arsenal for the massive amount of utility it provides, so Roy will probably want to use his Q rather than his W if possible to deny Sloth's R.

Sloth has massive potential to reach the backline with his massive movement speed with Q and W. Even if Sloth did not hate that Roy interrupts his R so casually, he would still be focusing him down all the time, it is just the most natural thing that comes to mind for the average player. As the Roy player, you should be aware of this as going out of your way to avoid Sloth's E, and kite Sloth. Roy is such tasty bait for Sloth with his low health that it can be useful to lure him out and waste all his spells, before knocking him away from his friends with W.

That all said, using W to knock Sloth the way you want him is trickier than on most characters. Landing a W on Sloth in the intended direction when he is using Q is very hard, and is generally not advisable. Even if you land it correctly, he will quickly make up the lost ground with Q's maxed movement speed anyway, while there is still tremendous risk to send him in the wrong direction. It is probably for the best for Roy to let a Sloth running away with Q go, especially when he can just W at any time with minimal warning.

Playing against Roy Mustang
Don't stand on top of the R and give it proper respect. Focusing down Roy should be a priority, just don't be so obvious about it that he knocks you back and punishes you for it. Roy is one of the single least intimidating alchemists for most characters to encounter alone, so feel free to go crush his tiny HP bar for gold. In a group setting, though, you will want to keep your distance if you don't feel you can pick him or one of his allies off with little to no risk, given he is one of the biggest alchemists necessary to dogpile you and kill you. He not only provides a sizable amount of the damage needed to kill you, he can drag you to the group or prevent your escape if he gets his knockbacks right. If possible, save your movement option to avoid his W, at which point you have little to worry about.

When defending an NPC, you want to focus Roy even moreso than usual to prevent him from getting close enough to the NPC to cast R. If he uses R on you instead of the NPC, you have successfully prevented the vast majority of his damage to the NPC. If he has already used R, do not keep relentlessly chasing him through the sewer/central, though. His damage has already been used and can no longer be prevented. It is very tempting to keep chasing him for the easy kill since kills feel good, but if your goal is to save the NPC, he should no longer be your priority after R has already been used.

Trivia

 * Roy is by far the most common alchemist to be picked up by new players before promptly leaving the game partially due to his difficult early game as well as squishyness. This phenomenon is dubbed "Roy Curse" by the player base.