You can use borax in your dishwasher to both clean the dishwasher and kill the roaches in the dishwasher.
Once you kill the roaches with the borax in the dishwasher by running the dishwasher through a wash cycle with the borax and hot water then you may have to take a vacuum cleaner and suck out the dead roaches.
Put some borax acid out underneath your dishwasher as well and clean the dishwasher out periodically making sure any food particles are not left in the dishwasher since the roaches will be attracted to the food bits that are left over from the dishes when they're washed.