1. Heat a large, deep skillet or Dutch oven over medium-high heat. Add the Italian sausage and cook, breaking it up with a spoon, until browned and cooked through, about 5-7 minutes. Drain excess grease if needed, leaving about 1 tablespoon in the pan.

2. Add diced onion to the pan and cook for 3-4 minutes until softened. Stir in minced garlic and cook for 1 minute until fragrant.

3. Sprinkle in Italian seasoning, salt, and pepper. Stir to coat the sausage.

4. Pour in the chicken broth and heavy cream. Stir well, scraping up any browned bits from the bottom. Bring to a gentle simmer.

5. Add the uncooked pasta to the skillet, stirring to submerge it in the liquid. Cover and reduce heat to medium-low.

6. Simmer for 10-12 minutes, stirring occasionally, until the pasta is al dente and the sauce has thickened. If the sauce gets too thick, add a splash of broth or water.

7. Stir in the spinach and roasted red peppers (if using). Let the spinach wilt for 2 minutes.

8. Stir in the grated Parmesan cheese until melted and the sauce is creamy.

9. Taste and adjust seasoning. Serve hot with extra Parmesan and red pepper flakes if desired.