Preheat the Oven
Preheat your oven to 375°F (190°C).
Combine Ingredients
In a 9x13-inch baking dish, add the frozen meatballs, uncooked pasta, marinara sauce, water (or broth), Italian seasoning, and garlic powder. Stir everything together to combine.
Cover and Bake
Cover the dish tightly with aluminum foil and bake in the preheated oven for 35 minutes.
Add Cheese and Bake Again
Remove the foil and stir the casserole. Sprinkle the shredded mozzarella cheese evenly over the top.
Return the dish to the oven, uncovered, and bake for an additional 10-15 minutes, or until the cheese is melted and bubbly.
Garnish and Serve
Let the casserole cool for a few minutes before serving. Garnish with fresh parsley if desired.