Blanch the broccoli florets in boiling water for 2-3 minutes, then drain and set aside.
In a large mixing bowl, combine cooked rice, shredded cheddar cheese, cream of mushroom soup, sour cream, and milk. Add garlic powder, onion powder, black pepper, and salt. Mix until well combined.
Gently fold the blanched broccoli into the cheese sauce mixture and transfer to a greased 9x13-inch baking dish.
Mix crushed buttery crackers with melted butter and sprinkle over the casserole. Bake in a preheated oven at 350°F for 25-30 minutes until bubbly and golden brown.
Let the casserole cool for 5 minutes before serving.