Just got a small mouse colony today, but bred rats/mice before.
Harlan Teklad 8604
Brown's Hamster Seed Mix
Leftovers

I'm going to be switching the Harlan because the petstore just discontinued it. I'm currently checking into different poultry feeds for the correct nutrient levels and ingredients to feed to the rodents. The hamster mix I use for several reasons. One, it gives them a little bit of stimulation, two, it can keep them healthier, with the necessary oils and such in the seeds that the blocks don't always provide. The leftovers are fed to add more variety (and stimulation), and because I'm a stickler for not wasting food.