It depends on the age, your budget and your dogs activity level. I have always tried to feed a dog food that is meat based...meaning at least the first 1-3 ingredients are meat...and the dog food does not contain..corn, wheat, maize, soy, or by-product meals. The better the quality of the food, the less you need to feed, and the less that comes out the other end. I've had very healthy dogs through the years...and would rather spend my money on high quality food...then pay the vet. Feeding a good food you avoid skin conditions, allergies, ear infections and the dog smells better.
As for food...? My last 2 Rotties were fed Orijen (all different flavors) and Acana Regionals (all different flavors) as well as some raw when I could get meat at a reasonable price, as well as slow cooker toppers (when I cleaned out the freezer), and fresh food such as eggs, fruits and veggies, sardines, yogurt,etc.