Just because someone is an only child does not mean that is the reason why there is roommate trouble. People are all different and sometimes they are not suited for being roommates.
The two roommates i didnt get along with each had their own set of problems. One wanted constant alone time with her boyfriend and her friends would sit on my bed till 2am while i was trying to go to bed. That girl or her friends (im not sure who) broke my laptop by pushing my laptop bag which was on my bed onto the floor due to them wanting my bed to sit on. I used my laptop warranty to fix the issue because i had no evidence outside of them constantly bringing it up to me. I just wanted the heck out of there as they had no boundaries.
The other was really bad depressed to the point where she was sleeping all day and slamming doors when i was on the phone. And studying all night, not letting me sleep due to never leaving the room. She also brushed her teeth in bed so i got sick due to her unhealthy conditions.
How is either one due to me as an only child and couldnt deal with having to share stuff. Both were out of my control.