If you're just looking for a garbage disposal for 1-2 snakes then you have lots of options. There are plenty of snakes out there that will quite literally eat themselves to death if you let them; Pituophis have to be near the top of the list in this regard. If you find yourself needing to dispose of a larger number of rodents then you'll want multiple snakes acting as second, or one larger species, so as not to end up with a morbidly obese animal.
I like using my bull snakes for clean up because they are on the larger side for colubrids. A big male can easily handle a couple medium rats and you will barely see a lump. I'll also offer second servings to the carpet pythons but pay special attention to their build and make sure they maintain healthy muscle tone. When I'm looking to retire breeder rats, the papuan python lends a helping hand. Just take care with any animal you nominate as garbage disposal, frequent overfeeding can drastically shorten their lifespan.