How to deal with an immature, annoying, ignorant, 18 year old roommate?

Next time you should just tell him all these things you posted here, or make the list and give it to him(LOL) and to grow up, then perhaps ask to switch rooms if he doesn't realize he's a total moron. If this fails beat him at his own game, he's obviously not very smart, so make his arguments seem really foolish and just walk away. Another option is to basically treat him like hes 5 and ask him to fix anything he has out of line, you can't possibly be so ignorant to ignore that, and feigning it would be pretty darn hard after a week.