In a large skillet over medium-high heat, heat oil; sauté sausage and onion 6 to 8 minutes, or until browned, breaking up sausage into smaller pieces.
In a 2-quart or larger slow cooker, combine sauce, green pepper, Parmesan cheese, garlic, and salt. Add sausage mixture and mix well.
Cover and cook on low 4 hours. When ready to serve, stir in mozzarella cheese.
Just before serving time, prepare toasts. Cut Hoagie Rolls along the “hinge,” then slice each half into desired size. Brush slices with olive oil and minced garlic, if desired, and place on prepared baking sheet. Bake in 350 degree oven for 1-2 minutes, or until golden brown.
To serve, spoon pizza dip onto toasts. Enjoy!