Sausage Casserole With Cheesy Rice and Squash

Name: Sausage Casserole With Cheesy Rice and Squash
Ingredients: 2 delicata squash ( 2 pounds total), halved crosswise, seeded, and cut into 1/2-inch-thick rounds; 3 tablespoons extra-virgin olive oil , plus more for drizzling; Kosher salt and freshly ground pepper; 8 ounces sweet Italian sausage , removed from casing, crumbled ( 1 cup ); 1 medium onion , chopped ( 2 cups ); 1 red or orange bell pepper , chopped ( 1 1/2 cups ); 1 1/2 teaspoons dried italian seasoning; 1/2 teaspoon red pepper flakes; 1 14.5 ounce can fire roasted, diced tomatoes; 3 cups cooked white rice; 12 ounces low-moisture mozzarella , such as Polly-O, cut into small cubes ( 2 cups )