We first meet Roy Mustang in chapter 4, tankoubon 1 of the manga. At that time, years have already passed since he first came in contact with the Elric brothers, but the storyline that the manga actively covers starts with the Elrics visit to Reole. Gaps of past events are covered from time to time in various other chapters.

     

The Roy Mustang we come in contact with is a Colonel within the National Amestris Army. He was born in 1885 (in the FMA world's own timeline) and he's 29 years old at the time. He's stationed at East City Headquarters, where he's in charge of a wide range of activities, from criminal investigations to routine inspections. It seems he works under direct supervision from Lieutenant General Grumman, an elder man who trusts and relies on him quite a lot -- and who also happens to be Riza Hawkeye's grandfather on her mother's side (as specified in the Perfect Guidebook 2).

Being one of the higher ranks in East City means Roy has quite a few men under his command. However, those closest to him can be count with just a hand's fingers. First Lieutenant Riza Hawkeye (his right hand and the person he's known for the longest time), Second Lieutenant Jean Havoc, Second Lieutenant Heymans Breda, Sergeant Major Kain Fuery and Warrant Officer Vato Falman. Roy's trust for these people and the trust they (in return) rely on him, is something that never ceases to amaze me. Check out the relations section for more.

We are still slowly learning things about Roy before he met the Elrics and even after that, there's a really big gap during his assignment at East City. However, everyone knows that one of the most important events in Roy's life had to be the Ishval War, were he, as the Flame Alchemist, was dispatched to serve as a human weapon by Fuhrer King Bradley, along with other National Certified Alchemists.

The first impression we could get out of Roy is of a man who isn't afraid to speak his mind in public. Something which should be a problem, since he talks aloud about a date or how the murder of one of his superiors would mean having a higher rank available for him. He also appears as a very confident man, sure of his own habilities and fairly easy-going.

And we couldn't be more mistaken. Roy's personality is in fact misleading by nature and it takes a whole lot more to know him than a couple of pages (or a dozen of chapters).