I'm going to hide or throw away my roommate's disgusting sweatshirt
What is wrong with the sweatshirt?
You might think it's fine, but I think it's too colorful.
You may disagree with your roommate's fashion choices, but you should still respect his property.  Even if you hate his clothes, throwing them away or hiding them is still a form of theft.
Revenge is sweet and I'm just doing what I want to do in my house.
Even if you want to do it, you shouldn't. It is theft and you could be charged.