I lived on campus all 4 years of undergrad and 1 year of grad school, so I had a couple roommates.
Freshman year: took a random roommate and it worked out pretty great. My only complaint was that she would have her alarm at full volume, slept through it for about 5 minutes, then hit snooze. Repeat about 5 times a morning. Thankfully I usually had an early class, so I was usually gone before this routine started.
Sophomore year: roomed with the same girl from freshman year. Only now we both had boyfriends and required the occasional bit of privacy, so she devised the hair tie on the doorknob (a little less obvious than a sock I guess). One day I get a screaming phone call from her that she was so sick and tired of me always hogging the room and I was a terrible roommate. Except I wasn't in the room. And rarely was except to sleep at night because my boyfriend's roommate was rarely around (he lived near campus and went home for dinner often and every weekend). Turns out she was leaving the hair tie on the door and never taking it off. So she would see it there and assume I was in the room again when no one was. Things were a bit chilly after that. She moved off campus the next year and we might have said hi to each other once or twice on campus.
Junior year: A new random roommate. Very nice girl who was rarely in the room the first semester. She stayed with her boyfriend or a friend about 28 nights out of the month. So, got the place to myself which was great. But apparently her grades started to sleep, so 2nd semester she was in the room unless she was in class or eating. For about a week. Then I come back to the room one day to see her rolling out a suitcase with the last of her things. She officially moved out and I had the place to myself. Loved it!
At one point, a girl came by because she was having trouble with her roommates and was told I had a half empty room by the RA. I will admit I shaded things a little - I have a boyfriend that I see all the time, I'm an early bird with 8am classes, I have people over often for studying or projects. I didn't want to go back to sharing!
Senior year: New random roommate. I had always been in one of those suites with 2 people in 2 rooms that are connected through the bathroom. Often people signed up in groups of 4. This time I was put in with a group of 4 where one had had to drop out unexpectedly. It was a little awkward being the odd one out, but by then I wasn't in the room much due to classes and study groups and work. And she was good and quiet. Except for the one time I came home early from work to find a toddler playing on my laptop. Turns out she had been babysitting for a friend in our room. It didn't bother me much except she hadn't warned me and I would have put some stuff away that he could have damaged or could have hurt him.
Grad school: On campus apartment with 2 bedrooms for 4 people. But you also got a living room, kitchen, and full bathroom. And we had the RA in our apartment, so we only had 3 people (RA's get their own rooms). And my roommate graduated mid year, so it was only the 2 of us for a semester! Awesome!
The only annoyance was the RA. She never did the dishes! Both sinks would be piled full and the counters around them (apparently all 3 of us brought a full set of dishes). Eventually roomie and I did them, but it got really annoying. She cleaned up her act (please don't hurt me!) the next semester when I guess she realized that the mysteriously clean dishes could only have been done by one person.
So, I've been lucky in never having a roommate that made me curse their existence.