Preheat the oven to 375°F (190°C). Lightly coat a 9x13-inch baking dish with cooking spray or a thin layer of oil.
Arrange a single layer of frozen cheese ravioli in the bottom of the prepared baking dish.
Spoon 1 cup of marinara sauce evenly over the ravioli, then sprinkle 1 cup of shredded mozzarella over the sauce.
Repeat with another layer of ravioli, the remaining 1 cup marinara, and the remaining 1 cup mozzarella.
Sprinkle the top evenly with 1/2 cup grated Parmesan. If desired, cover loosely with foil to prevent over-browning.
Bake in the preheated oven for 20–30 minutes, until the cheese is melted and the dish is heated through; uncover for the last few minutes if you want more browning.
Remove from the oven and sprinkle with fresh parsley, if using, before serving.