Cooking Pizza Casserole is a straightforward process, and following these instructions will yield great results:

1. Preheat Oven: Begin by preheating your oven to 350°F (175°C).
2. Cook Pasta: Boil the rotini pasta in a large pot according to package instructions, draining it once tender.
3. Brown Meat: In a large skillet, brown the ground beef or sausage over medium heat until fully cooked. Drain excess fat.
4. Combine Ingredients: Add the diced pepperoni, bell peppers, olives, pizza sauce, cooked pasta, and Italian seasoning to the skillet. Season with salt and pepper to taste.
5. Layer Casserole: In a greased 9×13 inch baking dish, layer half of the pasta mixture. Sprinkle half of the mozzarella cheese on top.
6. Add Remaining Mixture: Add the remaining pasta mixture and layer the rest of the mozzarella cheese on top.
7. Bake: Cover the dish with aluminum foil and bake in the preheated oven for 25-30 minutes.
8. Uncover and Brown Cheese: Remove the foil and bake for an additional 5-10 minutes, or until the cheese is bubbly and golden brown.
9. Cool Slightly: Remove the casserole from the oven and let it cool for about 10 minutes for easier serving.
10. Garnish: Optionally, top with fresh basil before serving.

These steps will lead you to a delicious Pizza Casserole that your whole family will adore.