It really is hit and miss I'm afraid. I had two roomates (first dropped out) and they were both great. The first one I had was more a friend of convenience (i.e. we probably wouldn't have been friends otherwise - just different views etc.) but my second (who I was very shy around at first and vice versa) turned out to be amazing and by the end of the year I was genuinely upset she was moving back abroad (erasmus). We still talk a bit though. She also spent a lot of her time asleep which helped with the recharging.
I'm not biased because other people in my halls had terrible roommates so I know both sides. If you get a good roommate, it'll probably help you come out of your shell and you could have a friend for life. If not, well, that's part of the university experience :P