Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the cooked rotini pasta, shredded chicken, broccoli florets, olive oil, Alfredo sauce, garlic powder, black pepper, salt, and red pepper flakes. Stir until everything is well coated.
Transfer the mixture into a greased 9x13-inch baking dish, spreading it evenly.
Sprinkle the shredded mozzarella cheese and grated Parmesan cheese evenly over the top.
Cover the baking dish with aluminum foil and bake in the preheated oven for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden brown.
Let it cool for 5 minutes before serving. Garnish with fresh parsley if desired.