Cook casarecce in well-salted water until just al dente. Reserve 1 to 2 cups pasta water, then drain.
Heat olive oil in a large pot over medium heat. Add sliced sausage and brown on both sides.
Add onion, garlic, thyme, basil, rosemary, oregano, and red pepper flakes. Cook for 2 to 3 minutes until fragrant. Season with salt and pepper.
Stir in crushed tomatoes, tomato paste, and 1 cup reserved pasta water. Bring to a boil.
Reduce heat to low and simmer uncovered for 15 to 20 minutes, or until the sauce thickens. Continue for about 5 minutes longer if needed.
Add cooked casarecce, Parmesan, and heavy cream. Stir gently until combined. Add reserved pasta water ¼ cup at a time if the sauce is too thick.
Taste and adjust seasoning. Finish with basil, Parmesan, and red pepper flakes if desired.