Begin by bringing a large pot of salted water to a boil. Add the tortini or fusilli pasta and cook according to package instructions until al dente. Drain and set aside.
In a large skillet over medium heat, add the mild Italian sausage. Use a wooden spoon to break it into chunks as it cooks. Sauté until the sausage is browned and cooked through, about 5-7 minutes.
Once the sausage is cooked, reduce the heat to low and pour in the marinara or Pomodoro sauce and pizza sauce. Stir to combine and let it simmer for a few minutes to meld the flavors.
Add the cooked pasta to the skillet with the sausage and sauce mixture. Stir well until the pasta is fully coated with the sauce.
Preheat your oven to 350°F (175°C). In a greased casserole dish, layer half of the pasta mixture. Top this layer with half of the pepperoni slices, half of the grated Parmesan cheese, and half of the shredded mozzarella cheese.
Repeat the layering process with the remaining pasta mixture, pepperoni, Parmesan cheese, and mozzarella cheese.
Cover the casserole dish with aluminum foil and bake in the preheated oven for 20 minutes. After 20 minutes, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Once baked, remove from the oven and let it cool for a few minutes. Serve warm and enjoy the delightful flavors of your Easy Pizza Casserole!