The recipe calls for bite-size pieces. That's pretty small - but it's an important note. Sweet potatoes are dense and hard, and take a substantial amount of baking time to break down and get to that sweetly soft perfection. The smaller you cut your pieces, the more likely you'll have finished potatoes along with your chicken. If you're looking for a specific "bite-size" measurement - cut your sweet potatoes into about 1-inch cubes.