Pizza Casserole

Name: Pizza Casserole
Ingredients: Salt , for pasta cooking water; Cooking spray , for greasing the casserole dish; 16 ounces dry penne pasta; 8 ounces Italian sausage links (raw or pre-cooked); 1/2 red bell pepper , seeded and chopped; 1/2 green bell pepper , seeded and chopped; 1/2 small red onion , chopped; 4 ounces baby bella mushrooms , trimmed and sliced; 1/4 cup black olives, sliced; 24 ounces (2 1/2 cups) store-bought or homemade marinara sauce; 1/2 cup grated Parmesan cheese; 1 teaspoon garlic powder; 1 teaspoon dried basil; 1 teaspoon dried oregano; 2 cups shredded mozzarella cheese; 4 ounces pepperoni slices