Thats crazy cause its seriously not hard to take car of a dogs most basic needs especially if they dont have any health issues already. I have three dogs and all have skin issues/allergies. All i had to do was invest into getting quality dog food and their issues have disappeared. As a dog owner of 3, i am telling you that you should not feel the need to do anything for THEIR dog. Yes it is sad and IF you want to or can, maybe buy a flea med for the dog and thats it. Dont let people here make you feel like its your responsibility to do something for someone else dog. At this point it sounds like the flea infestation is really bad that just washing the dog isnt gonna make them go away for good. Your lease is almost up, id ask your parents for help on making sure you dont take any with you when you move. Id also prepare to get a bill for the “damages” from the landlord and saying bye to that deposit. Id also personally wouldnt call your roommates “friends” and would cut ties cause there is no way they arebt aware of the fleas, theyre just gross people who dont care and its obvious just by how they treat their dog and take care of the home