Cockroaches harbor diseases like salmonella in their digestive tract, which get carried through the feces. Since cockroaches do not have a specific area to defecate, they end up dropping their waste anywhere, including on the food we eat. If you have roaches in your home, there is a high chance of ingesting cockroach excrement.
If you accidentally eat roach feces, you may fall sick. Roaches spread various types of diseases. You can contract any disease being carried by the cockroach.