I'm going to force my roommate to take a shower
Because they are starting to smell.
I will try to convince him to take a shower through nagging and insulting. The house is starting to smell.
Your roommate is disgusting for not taking a shower, he needs to bathe. Forcing someone to do something is also not the best thing to do. Ask him politely to bathe because otherwise he will stink up the whole house everyday.
I think I'll do just that.
You can always talk to him about the negative impacts of no self care. Lay it down smoothly and politely is possible.