Preheat the oven to 400°F (200°C) and lightly grease a deep 9x13-inch baking dish with 1–2 teaspoons of olive oil.
In a large skillet over medium-high heat, brown the Italian sausage or chosen ground meat with the Italian seasoning, breaking it into bite-sized pieces as it cooks.
When the meat is browned, turn off the heat and drain excess grease. Stir the marinara or spaghetti sauce into the meat until well combined. If not using meat, skip this step and use the sauce as-is.
Spread a thin layer of sauce on the bottom of the prepared baking dish.
Arrange half of the ravioli in a single layer over the sauce, overlapping slightly if needed. Spoon half of the remaining sauce mixture over the ravioli and spread to cover evenly.
Sprinkle half of the shredded mozzarella over the sauce layer.
Repeat the layers with the remaining ravioli, sauce, and mozzarella, then finish by sprinkling the 1/4 cup Parmesan cheese on top.
Cover the dish with foil and bake for 20 minutes. Remove the foil and bake an additional 10 minutes for fresh/defrosted ravioli or 20 minutes for frozen ravioli.
Let the casserole rest for 10–15 minutes before serving, and add extra Parmesan if desired.