Here's a little breakdown of the two brands we're discussing. I added the top 10 ingredients, the price of the biggest bag, and how much it costs per pound.

Natural Choice Chicken & Rice

Top 10 Ingredients:

Chicken Meal
Rice Flour
Ground Rice
Rice Bran
Poultry Fat
Oatmeal
Soybean Oil
Sunflower Oil
Natural Flavor
Dried Beet Pulp

40 Pound Bag: $30.99 works out to $0.77 per pound

Blue Buffalo Chicken & Brown Rice

Top 10 Ingredients:

Chicken
Chicken Meal
Whole Ground Brown Rice
Whole Ground Barley
Rye
Oatmeal
Chicken Fat
Whole Carrots
Whole Sweet Potatoes
Ground Flax Seed

30 Pound Bag: $39.99 works out to be $1.33 per pound

Nutro is much, much cheaper - but Blue Buffalo has better ingredients. You could start with Nutro and see how well Roxy does on it. I know many dogs that are fed Nutro and do fine on it.

Good luck!