In a large skillet, cook the sausage, mushrooms, pepperoni, green pepper, and onion over meduim heat until sausage is no longer pink; drain.
Stir in spaghetti sauce and Italian seasoning.
Bring to a boil. Reduce heat; simmer, uncovered, for 10-12 minutes or until heated through. Serve with pasta.
Cool remaining sauce; transfer to freezer containers. Freeze for up to 3 months.
To use frozen sauce: Thaw in the refrigerator overnight. Place in a saucepan and heat through.