Preheat oven to 400 degrees F. Lightly grease a 9x13 inch baking dish.
Cut half of your pepperoni into quarters.
Add tortellini to the baking dish.
Add 2 cups mozzarella, pizza sauce, quartered pepperoni, green peppers, onions, and mushrooms. Stir everything together.
In a small bowl combine the Parmesan cheese with the Italian seasoning.
Top the casserole with the remaining mozzarella cheese, whole pepperoni, and black olives, distributing them evenly over the casserole like a pizza.
Sprinkle the Parmesan mixture over the casserole.
Cover with foil and bake for 30 minutes. After 30 minutes remove foil and continue to bake for an additional 15 minutes or until cheese is fully melted.