"If you feed them, they will come." :ohmy: This is what I tell residents that have pest control issues. Fortunately our most common bug is flour bugs, but occasionally a unit will get roaches.
We have a housekeeping letter, but it's usually only used at annual inspection time. We can't do any unannounced or surprise inspections, but with my residents, usually a stern talking to (aka "Guilt trip") makes the difference.
Our next step is the non-compliance notice, then if the situation does not improve, we issue a For Cause notice that requires the problem cured within two weeks or else they must move out within 30 days. Only once has it come to the resident having to move out. Ironically, the resident cleaned the apartment to like-new condition at move out. If they had only cleaned up before they moved, they could have stayed.
Our rental agreement includes a pest control addendum which allows us to charge back extermination costs, but I find it much more cost effective to have the property cover it. A reputation for having an infestation is much more costly in the long run than paying for pest control. We also have quarterly inspections by a pest control company. Every year at budgeting time I consider cancelling the contract for lack of need, but I'm glad we still have it.