The roommate needs to use Frontline plus regularly to help not only eliminate adult fleas but also to keep any baby fleas from growing up to adult stages.
I typically use Zodiac Fleatrol floor spray which kills adult fleas and keeps baby fleas from growing up because it contains the insect growth regulator Precor.
Its safe to use around furniture.
Flea eggs can even hatch out down in the cracks in a hardwood floor.
Hope this helps you!
Cat Health, Behavior, Care Expert
30+ years cat owner, rescue, breeding, study of behavior & health care