Preheat the oven 425F and spray a 9x13 casserole dish with oil.
In a small bowl, combine buffalo sauce, olive oil, garlic powder, onion powder, salt, and black pepper.
In a large bowl, combine sweet potatoes with half of the buffalo sauce mixture until all of the sweet potato is covered.
Add the sweet potato to the baking dish and roast in the oven for 30 minutes, flipping the potatoes halfway. It's important to make sure the potatoes cook through.
Add the chicken and broccoli to the same large bowl, add the rest of the buffalo sauce, and combine well to coat the ingredients.
After 30 minutes have passed, add broccoli and chicken on top of sweet potatoes. Bake for another 20-25 minutes until the chicken has fully cooked.
Finally, sprinkle the casserole dish with cheddar cheese. Broil for 3-5 minutes until the cheese has melted.
Garnish with green onion.