How to Make It
Preheat the broiler. Place the rolls cut side up on a baking sheet. In a large skillet, heat the olive oil. Add the sausages and fennel and season with salt and pepper. Cook over moderate heat, stirring occasionally, until the fennel is deep golden and the sausage is cooked through, 15 minutes.
Mound the mixture on the bottom halves of the rolls, then top with the marinara and mozzarella. Broil 6 inches from the heat until the cheese is melted, about 3 minutes. Top with basil leaves, close the sandwiches and serve.