Preheat oven to 400'F. Spray bottom and sides of a 13 x 9" casserole dish.
Spread 3/4 cup of spaghetti sauce into the bottom the prepared casserole dish to cover the bottom. Arrange half of the frozen (keep frozen) in a single later over sauce; top with half of the remaining sauce and 1 cup of the mozzarella cheese. Repeat layers once, starting with ravioli. Sprinkle with Parmesan cheese.
Cover with aluminum foil & bake at 400 degrees for 30 minutes.
Remove foil; bake uncovered for an additional 10-15 minutes until bubbly and hot in the center.