Oh sweet jeebus - I have had two roommates who fit the douchebag category.
Roommate #1:
Now I am Christian. I believe in God and such, but I'm not gonna take my beliefs and ram it down your throat. Roomie 1 was a super-religious nutcase who decided it was his business to convert me to his denomination because what I thought and believed about how I should live my own life wasn't good enough. Even better - (and keep in mind that this is a freshman dorm studio where it is only one room) - lets decide we want to play a little game we like to call "Let's have bible study in the room and not ask your roommate if its OK!" Thats OK that your roommate has been on his feet all day in classes, then had to work that afternoon, and is really tired and just wants to lay down and take a rest! Noooooooo. That is unnaceptable because how sleepy you are doesn't matter when you're a god warrior! YAY!!!!

now don't get me wrong - like I said, I'm a christian. But I also know how to respect other people: how hard would it be to maybe move that to the student lounge so your roommate could get some sleep or maybe tell him before hand so there are no problems? Shortly after that I became his "pet project" as he was determined to convert a filthy heathen such as I and thats when enough was finally enough. :P
Roommate #2 was just a dick, plain and simple. One day i came home to find the toilet seat inexplicably missing. Considering my roommate was never in as is, I had no idea of finding out what became of it. Ignoring my notes about this, and getting tired of having to go into military squats just to take a shit TWO FUCKING MONTHS LATER i skipped my classes and work in the hopes of catching him at home. It worked. Boy howdy, wasn't it ever fun when I discovered that he'd taken off the toilet seat to the apartment to use as some kind of freaky dada-ist sculpture based art project rather than just buying one at Wal Mart? HOW TOTALLY UNSANITARY IS THAT SHIT!!?!
This was also the same douche who liked to play Counterstrike, crank the volume up to eleventy-bajillion and blast away at anything that moved without the respect of his roommate or the people next door or the people above him who constantly banged on the walls to turn that shit down. It's fun answering the door to screaming next door neighbors at 3 in the morning because he refused to put headphones on due to them taking away the "magic of the Counterstrike experience!" FUN FOR EVERYBODY!!!!!!!!
Jam it back in, in the dark.