Cook spaghetti according to package directions. Drain spaghetti.
Meanwhile, in a large skillet, heat oil over medium heat. Add onion; cook and stir 4-6 minutes or until tender. Add garlic; cook 1 minute longer. Stir in pumpkin, broth, cream, cheese, parsley, rosemary, nutmeg, salt and pepper; heat through.
Add spaghetti and chicken; heat through. Sprinkle with additional parsley and rosemary.