The one thing that's so sad about Roy Mustang is how the more the story goes in the anime, the more he is hated and almost in the end useless. He is important to the show because he is a helper to Edward and Alphonse in finding their bodies back. When they sent letters to Hoeheniems friends they saw on his letters, Roy Mustang had showed up. Mustang may seem cocky and mean, but he does truly care for the Elrics, telling them that only Edward can enter the military, knowing Alphonse about the soul transmutation and what not.
The man does tend to be rude, making fun of Edward and his 'height' problems. Even when they duel he provokes him with height jokes.
Colonel Roy Mustang isn't just great for helping the Elrics, but he is known as the Flame Alchemist. He has synthetic white gloves that has a transmutation circle in the color of red knited on it. All he does is snap his fingers to give a spark in which soon all he needs is to concentrate before condensing the oxygen and hydrogen, cauing an explosion. Roy is known to be a Hero from the Ishbalan War. To him it is far worse. After being in that war, he almost comitted suicide, almost tried human transmutation as well. Of course his friend Hughes had stopped him as well as Dr. Marco did in the war. This was the turning point for Roy Mustang in which he decided to get up the ranks, hoping to become Furher in hopes of changing their Country.
He does have many allies and most who see him as a great man. Riza Hawkeye, Jean Havoc, Heymans Breda, Kain Fuery, Vato Falman, Alex Louis Armstrong, Maes Hughes, and even the Elrics. Though, his relationship between him and Edward seems to spread away further and further each time. They always keep secrets from each other, hiding information from each other. Mustang does hate it when the Elrics don't go to him for help, in which he really does want to be helpful, even when he doesn't show it. Winry Rockbell even starts to have a disliking to him, finding out about the past of the Ishbalan War. Of course he is known to be an enemy of the Ishbalans and the military get jealous and suspicious since he is a young man already high at the ranks.
Putting this in white since I want to be careful. This will talk about the movie:
Another sad thing about Roy Mustang is he tends to lose a lot. He killed so many innocent by order, he loses his best friend Maes Hughes, and even at the end, he loses his left eye which is now covered by a patch. From his whole journey, he is ended up with almost nothing. The military changed into a parliment in which is dreams of becoming Furher came to a complete end. In the movie, he is even looked as pathetic. He in a way quit the military and later got his ranks changed and demoted from Colonel to Corporal. Another thing that really shows how much he hated his past was when Havoc and Breda try to talk him back during the winter, he tries to make fire with a match. Obviously that is a sign he has never used alchemy since that day of killing the Furher.
Though, in the movie when he does appear for action, they always still call him Taisa, regardless of his rank. It shows that he has been given such great loyalty to his subordinates. And even slightly in the movie, you can see Edward and Roy almost remake the past and almost forgive of the things that happen. Kind of what happen between Edward and his father.
In the manga, he is sometimes betrayed a more comedic Colonel. There are times where him and Edward always try to tease each other, even in harsh situations. Sad things happen to him still and even know he is dealing with hardships (Chapter 52). They did change a little bit things about his profile, but still he is known to be the Flame Alchemist. Hopefully they will show even more about him when they keep continuing the manga.
Colonel Roy Mustang is a determine man with a determine heart, hoping to change the way people live. It shows his ups and downs, his life and the horrible things that happen to him. Yet, he still does what he thinks is right.