Heat the olive oil in a large pot or Dutch oven over medium-high heat. Add the Italian sausage and cook, breaking it up with a wooden spoon, until browned and cooked through, about 5-7 minutes.

Add the garlic, Italian seasoning, and red pepper flakes and cook for 1-2 minutes, until fragrant.

Add the tomato paste and cook for 1-2 minutes, stirring constantly.

Add the rigatoni, diced tomatoes (do not drain), marinara sauce, and chicken broth. Stir to combine and bring the mixture to a simmer over medium heat. Cover with a lid and cook for 15-20 minutes, stirring every few minutes, until the pasta is cooked al dente and the sauce has reduced and thickened.

When the pasta is cooked, remove the pot from the heat. Stir in the heavy cream and parmesan cheese. Season with salt and pepper, to taste.

Garnish with fresh basil, optional. Serve warm.