There are many foods that are not safe to dehydrate, so be careful to whom you follow.
Rice and beans should be fine, as long as they are just plain. Not adding any butter, etc. to the rice or other things to the beans other than dry seasonings when you cook them.
There are some real crazy ideas about drying out there. No hamburger rocks, eggs, cheese, leftovers, etc. Just because you read it in a book doesn't make it so.