Nearly every student has something that troubles them--if it isn't rolls it's something else. One of my seniors is awesome at rolling and falling; he's one of the keenest breakfallers in the dojo despite being in his 60's. But don't ask him about nikyo. I roll like a brick, but I'm good (to the annoyance of my partners) at finding ways to regain my balance and stop a throw from working. Another of my seniors is really athletic and very good at throwing and falling, but is tearing out his hair over his ki tests. And so forth.
So when you're annoyed by the way some people seem to learn rolling instantly, you can comfort yourself by reflecting that sooner or later they, too, will hit something they can't readily learn.