Boil rotini as directed. Drain and set aside, reserving ½ cup pasta water.
Set oven to 375°F. Lightly grease a 9x13” baking dish.
In a large bowl, combine pasta, chicken, Alfredo sauce, garlic Parmesan sauce, 1 cup mozzarella, ¼ cup Parmesan, salt, and pepper. Add reserved pasta water if needed.
Spread mixture in prepared dish. Sprinkle remaining mozzarella and Parmesan on top.
Cover with foil and bake 20–25 minutes, until hot and bubbly.
Uncover and broil 2–3 minutes for a golden top. Watch closely.
Let rest 5 minutes. Garnish with parsley, if desired. Serve warm.