Preheat oven to 425°F. Cook sausage in large skillet on medium-high heat until cooked through. Drain fat. Sprinkle sausage in bottom of greased 13x9-inch baking pan. Top with spinach and roasted red peppers.
Mix flour, Parmesan cheese, onion, Italian seasoning and seasoned salt in small bowl. Beat eggs and milk in large bowl. Add flour mixture; beat until well blended. Pour over mixture in baking pan.
Bake 20 to 25 minutes or until set. Sprinkle with Cheddar cheese. Bake 5 minutes longer or until cheese is melted.