"Rolled oats" refers to oat grains that have been flattened or pressed to form flat flakes. They are commonly used in breakfast cereals or recipes for oatmeal. Full definition
If you don't like using protein powder, I suggest using 1/3 cup rolled oats instead for a natural source of protein and a more filling factor. (heathermcclees.com)
For myself, I put about a third of a cup of rolled oats in first and blend them into a powder. (aggieskitchen.com)