I've found that even though my lease said no pets, we had a seperate pet lease... when it said only 2 pets, I kinda freaked and asked what they thought of chameleons/lizards. The manager said that b/c they lived in a contained space (ie:cage) and that they were not dangerous (would likely not bite or kill anyone) that they did not count towards the pet policy. I know this is specific to my apartment complex, but I know that even college dorms sometimes make exceptions like that. As long as you don't have the roaches around when he comes by, you can claim that they arrived on some produce from the store this last time you went shopping. (My leasing office used that excuse when we saw a roach & they didn't want to come spray at a time convenient for us to get the animals out). You can claim that you trapped the roach and tossed it into the cham cage as a pesticide-free way of ridding the place of the roach... We all know you would never risk that with your cham, but your landlord does not.
Good Luck!! (and sorry your roommate was so sketchy about it)