Is it okay if I make my roommate pay for his past pranks?
What kind of pranks has he been doing?
He's been making the shower cold for two months
I under stand you want revenge for those pranks but pranking him back will lead to retaliation. If he continues pranking you, you should tell him to stop.
I can't tolerate him, he's getting away with it.
Then I think it's wise to finally stand up to him, do you want to keep taking cold showers? It would be worth talking to him about it, because just doing it back may cause conflicts between you. You deserve a warm shower, so it doesn't hurt to try!