My rats aren't eating their rat food?

I adopted a trio of rats, all around a year old. They were fed a seed mixture by their original owner. I wanted something healthier for them so I give them Oxbow's Regal Rat. However, they won't eat it! I give them lots of other stuff (fruits and veggies, uncooked pasta, rice, cereal and low protein dog food) so they aren't starving, but I want them to get used to the rat food because it's more nutritionally complete. Any suggestions?