OP: It was a mistake to remove the plastic bag from the smoke detector. You should have photographed it, then gone to your RA or other “official” to show them this criminal, safety violation.
Many people are allergic to smoke. One can actually contract serious lung ailments due to exposure to second hand smoke.
This is a serious matter that won’t be rectified by a simple talk with your roommate. You need a new room or a new roommate.