10 gallon is plenty of space for 2 rats. Add a wheel and you're set. A multi-level is cool too. Just put half of a cardboard shoebox in there, cut a hole the size of an empty roll of paper towel towards the front edge, stick the empty paper towel roll in there to use as a ladder, then put a little substrate on top of the shoebox and you're good. You might want to check that the rats are the same sex. You might end up with rat babies! Rats grow fast too. So, hopefully your snakes will eat soon!
Rats that age will bite, so you'll need to be careful petting them.