Heat the olive oil in a skillet over medium heat. Add the sausage meat and cook until browned.
Stir the marinara sauce into the browned sausage meat and season with salt and pepper to taste. Turn down the heat and simmer the sauce for 8–10 minutes.
Boil a pot of water. Add the spaghetti. Cook only until al dente, as indicated on the package, and drain.
Add the spaghetti to the skillet with the sauce, and mix thoroughly.
Transfer the spaghetti to a baking dish and top with the grated mozzarella. Place it in the oven for 12–15 minutes, or until the cheese is bubbling and golden brown. Top with chopped basil and serve.