Heat the oven to 400°F and coat a 9-by-13-inch baking dish with cooking spray.
Place the rotini and chicken in the dish, then add the Alfredo sauce, broth, milk, garlic powder, salt and black pepper.
Stir thoroughly, spread the mixture level and press the pasta and chicken beneath the liquid.
Seal the dish tightly with foil and bake for 45 minutes.
Uncover, stir and verify that the chicken reaches 165°F and a center noodle is tender; if the pasta is firm, reseal and bake for 5 to 10 minutes more.
Sprinkle on the Parmesan and bake uncovered for 8 minutes, then rest for 10 minutes before serving.