It is important to keep in mind that not everyone is in a mood to socialize at the same time. Roommates should have a semblance of understanding and respect for each other’s desires.
If your roommate has a big presentation tomorrow and needs to be well-rested and less stressed, it is not the night to have a 20-guest dinner party. Furthermore, not every pair or group of friends are compatible as roommates. Think hard about not just whether you get along with your friends but also whether you have similar living styles (night owl vs. early riser, etc.). Not being considerate or taking your friend-turned-roommate for granted can ruin a relationship.