Heat oven to 400°F. Cook and drain pasta as directed on package, using minimum cook time.
Meanwhile, in 12-inch skillet, cook sausage over medium-high heat 7 to 8 minutes, stirring occasionally, until no longer pink; drain. Add garlic; cook 30 seconds or until fragrant. Add spinach; cook 1 minute. Stir in tomatoes, oil, salt and pepper. Gently stir in mozzarella cheese.
Spoon sausage mixture into ungreased 2 1/2-quart casserole. Stir in cooked pasta. Top with Parmesan cheese.
Bake uncovered 15 minutes or until thoroughly heated. Top with additional Parmesan cheese, if desired.