I'm going to ask my roommate to not microwave smelly foods in the room
Is there a scent in the room now?
Yes, it smells like rotten meat currently.
I think that is a reasonable rule to have. People should be aware if they share a room with someone they have to be respectful of their surroundings.
I think he has a bad sense of smell and he can't tell what he's cooking smells like.
That's reasonable. Perhaps they could move the microwave to another room?