Bring a large pot of water to boil over high heat.
Meanwhile, cook sausage in a nonstick skillet over medium-high heat, breaking the meat into small pieces with a wooden spoon, until the sausage loses its raw color, about 5 minutes. Drain the sausage on a paper-towel-lined plate and set aside.
In a medium bowl, mix the ricotta cheese with salt and pepper; set aside. In a separate bowl, toss the mozzarella and Parmesan together until combined; set aside.
Add 1½ tablespoons of salt and the pasta to the boiling water and cook, stirring occasionally, until the pasta is just beginning to soften, about 5 minutes. Reserve 1½ cups of the pasta cooking water, then drain the pasta. Return the drained pasta to the pot and stir in the marinara sauce, sausage, and reserved pasta cooking water.
Pour half of the sauced pasta into a deep 13x9-inch baking dish. Drop large spoonfuls of the ricotta mixture evenly over the pasta, then pour the remaining sauced pasta over the ricotta layer. Sprinkle the top of the penne evenly with the mozzarella mixture.
Cover the dish tightly with aluminum foil that has been sprayed with nonstick spray. Bake until the sauce bubbles lightly around the edges, 30 to 40 minutes. Remove the foil and continue to bake until the pasta is completely heated through, 25 to 30 minutes longer. Sprinkle with basil before serving, if desired.
Notes
*If you'd like to make this dish ahead, wrap the prepared casserole with plastic wrap and then foil, and refrigerate for up to 2 days or freeze for up to one month. (If frozen, the casserole must be thawed completely in the refrigerator, about 24 hours, before baking). Be sure to remove the plastic wrap.
*You can also divide this meal into two 8x8-inch casserole dishes (each will serve 4). Eat one and freeze one!