Oxbow regal rat is a great one. I feed my rats that and Harlan Teklad (can only order online it seems). I like feeding a mix of two types because it gives them the option, and plus I know if one food is not as nutritionally balanced as the other, that they will balance out together. But it's totally not necessary to feed two types, either!
Also feel free to make a dry mix of healthy treats so they have some alternative food every now and then (feed a couple times a week). I use suebee's mix as a rough guideline. It's not nutritionally complete on its own, but it's an easy treat to give them when I'm too tired to make them some elaborate treat. Also, freeze dried fruits and veggies are great for those late nights when your rats are BEGGING for something besides a boring food block, but you're too tired to cut up actual veggies/fruit. Just remember to feed fresh foods too! Nothing beats a ripe banana or some brocolli, my rats say! Also, frozen veggies are a hit (especially on hot days).
Long post, lol, hope that helps though.