Why are so many dorm roomates sad and crying so often

Someone else can give more detail but that's the "emo loner" roommate trait. The roommates have various traits to do things like fixing an item, bringing food or throwing parties. I've only had one who has had it so far, crying and leaving notes before he moved out at the end of the semester. It sounds like you have had several.

There are people like this. I remember going to a summer camp where someone would cry every morning, irritating everyone else. That person was homesick.