Preheat oven to 375°. Cook rigatoni according to package directions; drain., In a large skillet, cook sausage, mushrooms and pepper over medium-high heat until sausage is no longer pink and vegetables are tender, breaking up sausage into crumbles, 8-10 minutes; drain. Stir in marinara sauce, Parmesan cheese and cream. Add rigatoni and toss to coat., In each of 2 greased 8-in. square baking dishes, layer one-fourth of the rigatoni mixture and one-fourth of the mozzarella cheese. Repeat layers. Bake, uncovered, until heated through and cheese is melted, 25-35 minutes. (Cover loosely with foil if tops brown too quickly.) Freeze option: Cool unbaked casseroles; cover and freeze. To use, partially thaw in refrigerator overnight. Remove from refrigerator 30 minutes before baking. Preheat oven to 375°. Bake casseroles as directed, increasing time as necessary to heat through and for a thermometer inserted in center to read 165°.