Bring a large pot of salted water to a boil. Add the orecchiette and cook until al dente, according to package instructions. Reserve 1 cup of pasta water before draining.
While the pasta cooks, blanch the broccoli rabe in boiling water for 2 minutes, then drain and rinse with cold water to stop the cooking process. Set aside.
In a large skillet, heat the olive oil over medium heat. Add the garlic and sauté until fragrant, about 1 minute. Add the sausage and cook, breaking it up with a spoon, until browned and cooked through, about 8 minutes.
Add the blanched broccoli rabe to the skillet with the sausage. Sauté together for 3–4 minutes. Add the cooked orecchiette and toss everything together. Use some of the reserved pasta water to loosen the sauce if needed.
Add red pepper flakes (if using), season with salt and black pepper to taste, and finish with a generous sprinkle of Pecorino Romano.