You need to get to know your sim (by observation).... for example;
I had one particular roommate, obviously must have been a mermaid, though she wouldn't admit it, who spent a lot of time swimming. She was also addicted to showering. I'm guessing one of her needs were to keep somewhat wet. Luckily I had two bathrooms in the house and she could shower/lounge in water whenever she wanted (kinda).
Suddenly, I got the message popup explaining that her needs weren't being met, and she may have to move if it wasn't fixed. I looked around the house to see what her complaint could be, and saw one of the showers were dirty. I had my sim clean the shower tub and a few minutes later I got another popup explaining she was more comfortable now, and thanked me for providing.
Apparently mermaid roommates need 2 shower areas. (at least this one did lol) and don't let one of those showers get dirty. He/she may complain.
You need to observe your roommates addictions. What do they do a lot? Another example.... I had a roommate that was overly addicted to cooking. I generaly knew where to find her. Chances are, she was in the kitchen making yet another cake. lol. If the stove broke down, she'd likely threaten to move.
