Begin by laying three strips of aluminum foil into the slow cooker as described above.
Reserve 1/2 cup of pizza sauce. In a mixing bowl, combine 2/3 cup pizza sauce and the egg. Stir in onion, green pepper, bread crumbs, Italian seasoning, garlic, Parmesan, and black pepper. Add ground beef and pork sausage. Mix well with hands.
Shape meat mixture into a loaf and place into slow cooker on top of aluminum foil strips. Cover and cook 8 - 10 hours on low or 4 to 6 hours on high. Center of meatloaf should be 170 degrees when done.
Spread loaf with reserved 1/2 cup of pizza sauce and mozzarella cheese. Cover and cook for 15 minutes or until cheese is melted. Lift meatloaf from slow cooker using foil strips. Remove foil strips and serve. Serves 8.