There's more to go but I'd say this much should do it.  Just make sure your room is clean and that there is no food and dirty clothes lying about, as they can contibute to horrible smell, with rotting and body odors.

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"We have nothing to fear but fear itself" | Rise
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But basically, the key is finding the source of the smell and eliminating it, I mean, thats all you can do, sniff around when your roomate isn't there.

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Well damn!

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Talk to your roommate about the smell.  And encourage him to help you get rid of it.

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Roommates an asshole lol.  But I seriously think he hasn't showered since last closed weekend.  It's been like a month or longer x_x;