Preheat oven to 425 degrees. 

Mix together sweet potatoes, 1 tbsp olive oil, and 1 tbsp garlic on a baking sheet lined with parchment paper. Bake for 35 minutes, stirring occasionally. Season with salt. 

Meanwhile, heat 1.5 tbsp olive oil in a pan over medium heat. Add onions and cook, stirring often, until shrunken to half the size and caramelized. Remove from pan. 

Sear sausage slices in pan. Turn off heat and add kale, stirring until it turns a bright green.  Meanwhile, cook pasta according to package instructions. 

In the pasta pot, heat the remaining 1.5 tbsp olive oil over a low heat and add the remaining tbsp of garlic. saute until golden, then add pasta, sausage, kale, onions, sweet potatoes, and parmesan cheese. Mix well, season with salt and pepper.