SAUCE: Heat oil in medium-sized saucepan over medium-low heat. Add onions and cook, stirring occasionally, until softened. Stir in garlic and cook one more minute.
Add sweet potato, butternut squash and vegetable broth. Increase to high and bring to a boil. Reduce heat to low, cover and cook until tender, about 15 minutes. Add margarine or butter and stir until melted.
Transfer to blender with remaining Sauce Ingredients and puree until smooth. Adjust seasoning. If too thick, thin with additional vegetable broth or water.
COOK MACARONI: Add macaroni to large stockpot of boiling salted water. Stir and cook until al dente, about 6-8 minutes.
ASSEMBLE: Drain cooked pasta and return to pot. Add sauce to pot and stir until hot and creamy, adding additional water or stock if too thick. Serve immediately.