Misty -- doesn't your supplier sell both rats AND mice? Mine do, I buy rats for Marbles & get them in the same box with the mice. I've bought from several places that way. There's a little more variation in rat size than I would like (some "small" rats were a little smaller than I would prefer but I can always offer 2 small ones to Marbles, and if he will eat at all he will take multiples if they are very, very hot [actually hotter than a live animal would be]). I would think, though, that if you watched your corn for excessive weight gain, you probably could feed properly sized rats. I offer rat pinks (because I bought them because one of my 09s prefers his food furless and he's too big to live on pinks) as meals for my 09s and everybody takes them and nobody seems to be too fat, but if I feed a rat I wait a little longer than the usual interval before the next meal. So instead of 5 days I wait 7, and offer a fuzzy mouse the next time. Except Sailor Sam, who won't eat food with fur so he gets a rat pink every 7 days dusted with calcium powder because pinks don't really have enough calcium, and he seems to be growing, shedding & pooping properly on that regimen. I'd like to get him onto mice, though.
So yeah, with proper attention to avoiding obesity, I bet you could feed rats. I'd see if your rat vendor has mice, though, because shipping is the big cost in buying frozen rodents, and if they can travel in the same box with the rats, mice should be reasonably priced.
