I'm going to lock my roommate in for 20 minutes and refuse to go get a spare key.
Why are you locking your roommate inside?
I can explain it to them when they're in there.
You shouldn't impede your roommate's actions. If they want to go, they should go.
Nah, I will yell at them and then they will stay in there.
There is an easier way to converse with your roommate, as locking them in will only create tension and conflict. Let your roommate know that you need time to work things out with them instead of using force.