Preheat your oven to 375 degrees F. Bring a large pot of salted water to a boil and cook the gluten free ziti for 2 minutes less than the package directions so it's slightly underdone. Drain and set aside.
Heat the olive oil in a large oven-safe skillet or Dutch oven over medium-high heat. Add the sausage, breaking it into crumbles, and cook for 6 to 7 minutes until browned and cooked through. Add the garlic and cook for 30 seconds.
Pour in the marinara sauce, stir to combine with the sausage, and remove from heat.
In a medium bowl, stir together the ricotta, egg, basil, salt, pepper, 1 cup of the mozzarella, and 1/4 cup of the parmesan until well combined.
Add the cooked pasta to the sauce and toss to coat. Dollop the ricotta mixture over the top and use a spoon to gently fold it through the pasta, leaving some pockets of ricotta throughout rather than fully mixing it in.
Transfer to a 9x13 baking dish if not already in one. Sprinkle the remaining 1 cup mozzarella and 1/4 cup parmesan evenly over the top.
Bake for 25 to 30 minutes until the cheese is melted, bubbly, and golden brown on top. Let it rest for 5 minutes, then garnish with fresh basil and serve.