My roomates dog keeps peeing and pooping on the couch?

My roomate has a dog and I have 2 cats, they all get along great, play and roll aroud, but for some reason the dog won't stop doing his business on my suede couch. I clean it up and have even tried using cleaners on it, the smell won't go away and it's ruing my couch. the cats both use their litter box, and we let the dog out numerous times a day. My roommate thinks its not fair to crate her dog while the cats roam freely through the house. Does anyone have any suggestions?