My cat is stuck in the middle

I’m leaving my current situation by the 31st, my cat has taken somewhat of a liking to my roommate whom I am no longer friends with and don’t speak to anymore. How do I communicate to said roommate that my cat is no longer allowed in his room?

He reinforced the behavior and maybe it’s on me for not setting boundaries sooner and maybe I’m overreacting and should just tough it out until I leave. But I hate that my cat goes in there.. HELP