Preheat and Prepare: Set your oven to 350°F and lightly grease a 9x13-inch baking dish with cooking spray or butter.
Create the First Layer: Spread 1½ cups of tomato basil sauce on the bottom of the prepared baking dish, then arrange one bag of frozen ravioli in a single layer over the sauce (about 19 ravioli).
Add the Second Layer: Top the ravioli with another 1½ cups of sauce, then layer the remaining bag of frozen ravioli on top in a single layer.
Build the Cheese Layers: Spread the remaining 2 cups of tomato basil sauce over the second layer of ravioli, then sprinkle the 1½ cups of mozzarella cheese evenly across the entire casserole.
Top and Season: Finish with the ½ cup of mozzarella and the ¼ cup of parmesan cheese sprinkled generously over the top, then cover the dish tightly with foil.
Covered Bake: Place the foil-covered casserole in the preheated 350°F oven and bake for 25 minutes, allowing the ravioli to cook through and the cheese to begin melting.
Uncover and Brown: Remove the foil and continue baking for an additional 5 minutes until the top is golden and bubbly, and the cheese is melted and slightly browned.
Rest and Garnish: Let the casserole rest for 5 minutes after removing from the oven, then sprinkle the fresh parsley over the top for a vibrant finish.