Pet stores carry rat food...
They will eat almost anything, (bird food, hamster/gerbil food) but you want them to be healthy. They can eat UN-sweetened cereal, and dog food, preferably low fat senior, not cat food as cat food has too much protein. Lots of grains, dry pasta, fruits and veggies.....
Just remember to read labels!!
Rats only need about 5 percent fat --this means pick out the sunflower seeds
and about 14 percent protein from what I remember....you may look it up.
MORE DIETS HERE:
http://www.ratsrule.com/diet.html
http://www.dapper.com.au/articles.htm
Here is more info from:
http://www.wikihow.com/Care-for-a-Pet-Rat
# The staple diet of your rat should consist of lab blocks or a homemade grain mix called "Suebee's Diet" and dog food. The recipe can be found online..
The rest should be supplemented with fresh and frozen fruits, veggies, cooked beans, seeds etc. Avoid giving citrus juices to male rats, as a chemical in the peel (which is usually in commercial citrus juices) binds with a protein in their kidneys, and causes cancer. Fresh citrus is fine, as long as you remove any skin and pith (the white stuff) before feeding male rats. Females do not have this problem.
If you must purchase commercial rat food be aware that the corn and alfalfa pellets are undigestable and small seeds will likely go uneaten. Many vets recommend Oxbow Regal Rat, Mazuri, or Harlan Teklad lab blocks.
# Make food readily available. Rats will stop eating when they are full. Buying pre-made "rat mixes" isn't necessarily the best choice as some rats will eat only the pieces they enjoy and leave the rest. Some recommend buying "lab blocks" which are "nutritionally complete" and supplementing with fresh fruits, veggies, dry bread, yogurt. Rats may become bored eating the same thing every single meal, and can stop eating. Dog food made for Seniors (which has a lower fat content) can be a good supplement to their regular diet.
# When buying rat food, ensure that it is not just seeds and nuts! These mixes contain too much protein and fat for rats. Also ensure that corn is not the number one ingredient in the mix as too much may contribute to cancer. Instead of searching for a good rat mix, you can choose to make a homemade mix such as Suebee's (see external links).
Best of luck--Rats Rock!