From what I've found is you can't always roll when you're holding other buttons down, such as fire or thrust. Is it just the keys aren't working at all, without pressing anything else?

The only problem you could have is if those keys assigned as hot-keys within windows, and the button combo is interfering with that; but that really shouldn't affect the game either.

Have you tried restarting a new game, re-installation etc? Maybe something bugged when that was taking place.

You could attempt to patch it, even though the one on GOG is up-to-date, though I expect attempting that will yield little change, and might just bust the game. At least you could install it again, but don't forget to back up your saves if you start fiddling around.