So I spent a couple of hours researching PA law just to make sure, but no, they are not allowed to withhold rent just because they have roaches. There is a long drawn-out process which, if they followed it, could eventually lead to them being able to legally withhold rent, but they would have to prove the roaches weren't their fault, and I know they can't do that.
I am giving them just ONE chance to get the situation straightened out. Their lease is up in November and if they are still living in filth, they'll have to leave. Technically I could evict them now, but I hate going through the hassle.
I wonder if the tenants in the other side would like to buy the whole house and take us out of our misery?