Bring a large stock pot of water to a boil then generously salt with kosher salt. Add pappardelle pasta and cook until al dente then drain, reserving 1/2 cup pasta sauce.
While pasta is cooking begin cooking the sauce. In a 10-inch skillet over medium-high, heat olive oil and then add red bell pepper slices and onion and cook for 4-5 minutes or until onion softens, stirring occasionally. Season with kosher salt, add mushrooms and cook for another 3 minutes. Add garlic, turkey sausage and red pepper flakes and cook until turkey is warmed through, about 3 minutes.
Add cream, marsala, tomatoes and rosemary to skillet and cook for about 3 minutes or until sauce thickens and tomatoes soften. Gently fold in pasta to skillet until coated. If you'd like more sauce, add reserved pasta water one tablespoon at a time or another pour or two of cream if you want a heavier sauce. Garnish with parmesan, kosher salt and more rosemary if desired. Serve immediately.