Cook pasta according to package instructions to al dente. Save 1 cup pasta water.
While the pasta is cooking, shred or cube the rotisserie chicken.
Preheat the oven to 350 degrees. Prepare the casserole dish, and set aside.
Spread the shredded chicken evenly on the bottom of the casserole dish.
Add the cooked/drained pasta over the chicken.
Pour the Marinara sauce and slightly mix to coat the pasta. (If you prefer you can place the cooked pasta into the Marinara sauce and mix to combine. Once the pasta is all coated, pour over the chicken and spread evenly). Add enough pasta water to ensure the pasta is good and saucy.
Sprinkle 1 cup of shredded mozzarella cheese over the pasta, then sprinkle with the garlic and onion powder.
Evenly sprinkle the breadcrumbs over the pasta, and top with the remainder of the shredded mozzarella. Finish by adding the Parmigiano.
Bake in a preheated oven for 25 to 28 minutes or until it is nice and golden brown.