Grill the Italian sausages for about 10-12 minutes, turning occasionally, until fully cooked.
While the sausages are grilling, toast the hoagie rolls on the grill for 1-2 minutes until lightly browned.
In a small pan, heat the marinara sauce over medium heat.
Once the sausages are cooked, place each sausage in a hoagie roll. Top with marinara sauce, shredded mozzarella cheese, bell pepper slices, and onion slices.
Serve hot and enjoy!
Notes:
Feel free to add any other toppings you like, such as jalapenos or olives.