If you are buying fruits at a market they shouldn't have enough traces of pesticides to make them sick. Pesticides are poisonous, it's that simple. They don't just kill "bugs" the will kill any animal that ingests them. So, the fruit you buy should have low enough levels for human consumption then they should be low enough for cockroach consumption. Having said that I wash my own fruit but if you are concerned about your fruits and veggies you should wash them for your own safety first.