Cook the pasta according to package directions, omitting salt and fat; drain.
Remove casing from sausages. Shape sausages into 12 (1-inch) balls. Heat a large skillet over medium-high heat. Add oil to pan; swirl to coat. Add meatballs to pan; cook 7 minutes, browning on all sides. Remove the meatballs from pan. Add onions, red pepper, and garlic to pan; sauté for 2 minutes. Return meatballs and add marinara sauce to pan, and bring to a simmer over medium heat, scraping pan to loosen browned bits. Reduce heat to medium-low, and simmer 5 minutes or until meatballs are done. Add pasta to sauce mixture; toss well. Sprinkle with cheese and basil.