Bring a large pot of salted water to a boil. Add the gemelli pasta and cook according to package instructions until al dente. Drain and set aside, reserving 1/2 cup of the pasta water.
In a large skillet, heat the olive oil over medium heat. Add the Italian sausage, breaking it up with a wooden spoon, and cook until browned and cooked through, about 5-7 minutes.
Add the minced garlic to the skillet and sauté for 1 minute until fragrant.
Stir in the asparagus pieces and cook for about 3-4 minutes until they are tender but still crisp.
Pour in the chicken broth and heavy cream, stirring to combine. Bring the mixture to a gentle simmer and let it cook for 2-3 minutes to thicken slightly.
Add the cooked gemelli pasta to the skillet, tossing to coat in the sauce. If the mixture seems dry, add some reserved pasta water until you reach your desired consistency.
Season with red pepper flakes (if using), salt, and pepper to taste. Stir in the grated Parmesan cheese until melted and well combined.
Serve immediately, garnished with fresh parsley.