Preheat the Oven: Preheat to 350°F. Spray an 8×8-inch baking dish with cooking spray.
Cook the Rigatoni: Prepare the rigatoni according to package instructions for al dente texture. Drain and drizzle with olive oil to prevent sticking.
Sauté the Sausage: In a large skillet, heat olive oil over medium-high heat. Sauté the onion and garlic until translucent. Add the Italian sausage, cooking until browned and thoroughly done. Stir in basil, salt, and pepper, then set aside.
Make the Roasted Garlic Alfredo Sauce: Roast the garlic and squeeze it from its skins. Mash the garlic. In a saucepan, melt the butter over medium heat. Add the heavy cream and roasted garlic mash, warming without letting it boil. Whisk in grated Parmesan cheese until melted and smooth. Stir in the flour-cream mixture to thicken the sauce. Adjust seasoning with salt and pepper.
Combine & Bake: Toss the cooked sausage and rigatoni with the Alfredo sauce until everything is well coated. Transfer to the prepared baking dish, sprinkle with shaved Parmesan cheese, and bake for 30 minutes, until bubbly and golden brown on top.
