Mostly, the manga and Brotherhood are pretty similar (with some notable exceptions like the Ishval flashback and the early episodes/chapters). But there are some small scenes that play out differently as well. This is one such scene.
In Brotherhood, Roy is shown still determined to become Fuhrer. In the manga, the scene takes place much sooner after the battle, and he is told by Dr. Knox that blind soldiers have to retire. This makes perfect sense, because a blind soldier cannot fight. Roy manages with Riza’s help during the Promised Day, but it’s impractical, and in fact dangerous, for him to continue using his alchemy offensively while blind.
What I really like about the manga, though, is that it shows that even if Roy can no longer become Fuhrer, that doesn’t mean that he is giving up any of his desire to atone for Ishval. He is still clearly determined in the second panel. And I think it has more impact than Brotherhood, where the issue is largely sidestepped.
I also wonder, what would Roy have done, had he been forced to leave the military?
When Envy caught sight of Hughes’ photo that fell from his pocket whilst in the phone booth before his murder, he was originally going to change himself into Elysia instead of Gracia. He then realized if he took the form of a small child, he might shoot the Lieutenant Colonel in a non-fatal place due to how short he would become and result in Hughes surviving the attack.