Seeing as I've been following Fullmetal Alchemist for quite some time now (since around the end of 2003) and unfortunately for my brain and the sake of my sanity I've been in contact with the fandom more than I should have, I figured I'd use some space to answer all those annoying repetitive questions about Roy (and about the series in general) that seem to always come back to haunt me.

Note that the regular FAQ page for the shrine is located here.

I thought Fullmetal Alchemist was an anime, what the hell.
Uh, no. Fullmetal Alchemist the manga began its serialization in August 2001 in the Monthly Shounen Gangan magazine. You can read more about it here. Around September 2003, the BONES anime studio made a 51-episodes (loosely based) adaptation of it.

Who the hell are you talking about here? This is not the Roy Mustang I know!
Aah, another poor soul deceived by BONES' evil doings. There, there... it's okay, just go pick up the manga and everything will be all right again. If after reading the manga you're still confused, take care of erasing your memories about the anime, that should do the trick.

I still think you're wrong. I don't even think the anime and the manga are that different.
Lucky I'm the one who gets to write here then.

How old is Roy? When and where was he born?
When he's first introduced (when the Elric brothers arrive to East City in chapter 004), Roy is 29 years old. He's supposed to have turned 30 around tankoubon 11. He was born in 1885, but the exact date or place of birth is unknown.

How does Roy's rank evolve? I'm confused.
National Alchemists receive the rank of Major in the military as soon as they pass the exam and they're given their license. That's seven ranks more than corporal right off the bat. After the Ishval War ends, he's stationed in East City and by the time he meets the Elric brothers, he's been promoted to Lieutenant Colonel (probably due to his services at the war). When Edward Elric goes to East City after having his automail surgery done, Roy has been promoted again to Colonel. This is his rank nowadays too (five below the Fuhrer himself, if you're curious).

Roy's destinations in Amestris confuse me too.
It's easier than it looks. We've got still no clue about what Roy was doing before Ishval. Then he went to war. After that, it looks like was transferred to East City. He and Hawkeye see Edward to Central City to take his National Alchemist exam, but that was no transfer, of course, Roy and the rest are still in East. It's in tankoubon 06, after Hughes' incident, when Roy is finally assigned to Central City, taking his team along with him. In tankoubon 13, when Roy finds out the truth about the Fuhrer, each one of Roy's subordinates are given a new transfer (except Hawkeye, who is to be the new personal assistant to the Fuhrer himself). We still don't know what the outcome of this will be.

What about Roy's family?
Still no idea.

When and how did he meet Hawkeye/Hughes/Havoc/Breda/Fuery/Falman?
Although we haven't (yet) seen the exact moment when he meets any of those people for the first time, we now know approximately when. We can suppose he met Hawkeye at some point before he entered the military, as her father was his alchemy teacher. He wasn't even the Flame Alchemist by then. It looks like he met Hughes at the military academy. He met and recruited the others after the war, when he got stationed in East City.

What color are Roy's eyes?
Blackity black black.

You forgot to say that Roy tried to kill himself / killed Winry's parents / likes to get drunk randomly / lost an eye / went emo and fled to the north.
Uh, what.