Okay I have been thinking that to get back his sight Roy might have possibly given up alchemy in the end too.
Okay yes I know he used Marcoh's philoshoper stone but would that have given Roy his sight back and got him out of the doors.
If you remember in the chapter Roy says I wish I could do what Fullmetal did and use my own door as a toll but then there wouldn't be a way back. Of course then Marcoh holds up the philosopher stone and says can use this a toll. But would that have been enough to get his sight back and to get him back from the doors?
Al exchanges his soul for Ed's arm and is stuck in the doors. Ed gives up his doors to get Al and him out but he doesn't get back the leg he lost. I am also thinking of the time Ed uses Envy's philosopher stone to get them out of Gluttony. It seemed he could only use that as a passage fee and that was not enough to get anything he lost back.
Of course maybe I am thinking about this too much. I guess if Arakawa wanted us to think Roy couldn't use alchemy anymore she would have said as much but I don't know it just something that suddenly came to me.
edit Okay schellibie pointed out a logical reason why this theory is wrong. The reason why Roy said he would not be able to get back if he gives up his alchemy is because he would have to give up his doors and then he would have no way out. Ed was able to get back because he went through Al's doors. So yeah I am wrong. :)