Cook the pasta in a large pot of boiling salted water until it is barely al dente. Don't overcook! Drain.
Preheat your oven to 350°. Spray a 9x13"
While the pasta is cooking, cook the ground beef, sausage, and onion in a large skillet over medium high heat until the meat is brown. Drain off the fat with a paper towel.
Add the garlic and saute for 30-60 seconds, just until fragrant. Stir in the marinara sauce, pepperoni, parmesan cheese, Italian seasoning, and the cooked rotini noodles.
Spread the mixture into your prepared pan. Sprinkle grated mozzarella cheese over the top.
Cover the dish with aluminum foil. (I like to spray it with cooking spray.) Bake at 350° for 25-30 minutes, or until dish is bubbly and cheese is melted.
Notes
You can use either homemade or store bought marinara sauce.
Feel free to add any of your favorite pizza toppings!