What ar Rotel tomatoes?

Rotel is the brand name. They are basically diced tomatoes mixed with green chilis, onions and Mexican spices. There are also store brands of the same thing that usually cost a few cents less.

Rotel is the brand name for tomatoes canned with peppers and onions.

They are like a (pretty) hot salsa in a can. It is chopped tomatoes, and chilis. You can find it either where you find canned tomatoes or in the Mexican food aisle of most supermarkets. It is a pretty common item. For some reason, only Rotel makes it.