Hi ten rats later! Oxbow adult rat food seems to be the preferred food by most people. Also if you go to the forum tab, then find rat health, there is a sticky called good and bad food for rat. There also loads of information in other stickys. Welcome to the forum! I also have ten rats, lol.
I give my rat Oxbow Regal and also fresh veggies/fruits. They get a little of every fresh veggies, greens, fruits from the salad bar of my grocery store- it usually is 8-12 different produce. I add a little flax seed oil and they love it!
Oxbow is pretty good as commercial foods go, though I prefer a decent home made mix. If oxbow was available for less than £30 per kg here I'd probably add some to my mix though (which is high praise as I don't like pelleted/block style foods).