Your room mate obviously loves this cat, and obviously takes care of the cat as he suffers with some conditions. id like to ask you some questions
who owns the house? the cat owner?
why is the cat allowed the run of the house?
why is there not a cat flap on the door so he can come and go as he pleases?
if your only renting off somebody, why isn't your room locked
cat should have his own room, utility/laundry room etc
i have two cats myself, and i love them to death, but they know there place, they have their own room with cat flap and they come and go as they please, i would never allow them to take over the house and sleep where they like, i think you should discuss this with your room mate, thats the only problem i see here, do not do anything cruel to this cat, someday you will have a pet, and if anything ever happened to it, you would be devastated. whats worse..iving with the cat who can be confined, or living with a upset bitch