It really depends on the college and their dorms. My freshman year I shared a room with one other girl. We had a bathroom that connected to a room with two other girls. Sophomore year I was in a dorm that was an apartment, 4 bedrooms and 2 bathrooms. My school had no dorms with floor bathrooms, however I did almost go to a school that did. My school would consider
co-
ed rooms on a case by case basis and both people had to agree, same with the apartments.
As for roommates, again it depends on who you get. My roommates freshman year became my best friends. But I also had roommates that were messy, inconsiderate, and loud. For my school, if you really didn't get along then they'd have a mediator try to help. If things were still really bad they would let you move if there was another open room somewhere.