Some smells that roaches hate and the smells that will repel roaches are Lavender, Citrus and Eucalyptus.
The roaches hate those smells and will avoid areas where those smells are.
Dawn Dish Soap and even bleach will kill roaches near instantly or get some roach spray and it too will kill roaches and another good way to get rid of roaches is to remove any food, dishes etc and turn off the electricity in your house and use a fog canister for roaches to fog the house and kill all roaches in the house.
If roaches do contaminate your food you need to throw the food out because it can make you sick to eat food that has been contaminated with roaches even when you heat the food up.
When roaches contaminate food the food should really be thrown out and not eaten.
Although heating of the food that the roaches contaminated should kill the germs from the roaches as long as you heat the food hot enough it's still not worth the risk to your health to eat the food that the roaches have been on.
When roaches contaminate food it's best to throw it out.
You could still become sick from eating the food that the roaches contaminated especially if you haven't heated up the food hot enough.
Heating the food up to 400 to 500 degrees or more should kill the germs that the roaches left on the food but still it's not a good idea to eat the roach contaminated food.
There could also be some dead roaches or dead roach eggs in the food even though you may not be able to see the roaches or roach eggs.
If you have a roach infestation I would recommend hiring an exterminator to kill the roaches.