Preheat the oven to 350 degrees Fahrenheit.
Lightly spray a 9"x13" pan with nonstick cooking spray.
In a skillet over the stove top, cook Italian sausage with minced garlic, breaking it up into small pieces, until no longer pink.
Stir in drained Italian diced tomatoes.
In the prepared pan, spread the meat and diced tomatoes mixture evenly on the bottom.
Add cooked, drained pasta over the top of the meat.
Sprinkle 1 c. shredded parmesan evenly over the pasta.
In a large bowl, stir together Alfredo sauce and marinara sauce. Pour it evenly on top of the cheese and pasta. Spread it a little so it seeps into the pasta. Dish will be full.
Bake it, uncovered, for about 30 minutes, or until bubbly and completely heated through. Then, top with 2 c. shredded mozzarella and return it to the oven for about 5 minutes, or just until the cheese is melted. Serve immediately.