There are several ways to feed a rotation diet. You can stick with the same brand and rotate flavors, or you can change brands. Or you can even rotate between kibble, canned, raw.
I feed a rotation diet, and switch both brands and flavors. I usually rotate between three, trying to include the three food groups: Poultry, Red Meat, Fish. I feed a specific food for one month and rotate to the next. Hope that makes sense. When rotating to a different food, I'll mix a bowl of 50/50, but the new food always gets eaten first.
Do save a few protein sources in case you ever have to deal with allergies.