I am currently switching back and forth between rats and mice for yearlings and adults. The hatchlings just get the mice though. If you try searching for diet and food you might find some thread that discuss this more in depth. I know there have a been a few that discuss different varieties of rodents that are offered to corns. Such as hamster, gerbil, rat, mouse, and some others I can't think of.
A lot of it depends on the size of the snake and the snake's personal preference. I have some snakes that turn their noses up at rats and others that turn their noses up at mice once they have tasted rat.
Again, you'll probably find more information using the search function then I can offer though, and I am far from an expert - I mostly just sit back and try to learn everything I can with all the other newbies.
Jenn