Cook meatballs according to package instructions.
Bring large pot of salted water to a boil. Add broccoli rabe and cook until crisp-tender, about 2 minutes. Transfer broccoli rabe to bowl of ice water; once cooled, drain and set aside. Add pasta to the pot of boiling water; cook al dente.
Melt butter in 4-quart stockpot over medium-high heat. Sauté garlic in butter 1 minute.
Stir in cream; bring to a simmer, stirring constantly. Add cheese; stir until completely melted and sauce thickens. Season with salt and pepper to taste.
Add meatballs and broccoli rabe to sauce. Drain pasta and toss with sauce.