Heat the oil in a large skillet over medium heat. Add the sausages and cook until brown on both sides, about 7 to 10 minutes. Remove from the pan and drain.
Over medium heat, add the peppers, onions, salt and black pepper to the pan and cook until golden brown, about 5 minutes. Add the oregano, basil, garlic, and red pepper flakes and cook 2 more minutes. If desired, add tomatoes and/or tomato paste, stirring to combine. Bring to a simmer.
Cut the sausages into 4 to 6 pieces each, about 1-inch slices. Add the sausages back to the pan and stir to combine. If using sauce, cook until it has thickened, about 20 minutes.
Fill hoagie rolls with sausage mixture; serve immediately.