Heat oil in a large skillet over medium heat. Add sausage and onions, cook 5 minutes or until onions are soft and translucent. Add garlic and red pepper flakes and cook 2 more minutes until fragrant. Add broth, tomatoes, milk and pasta:bring to a boil, then cover and simmer 15 minutes or until pasta is desired tenderness. Stir in salt and pepper and stir in cheese until melted and smooth.