1. Preheat oven to 400 F.
2. Line large baking sheet with parchment paper; set aside.
3. Place sausage, kale, onion, bell pepper and sweet potato in a large mixing bowl; drizzle with oil and season with salt and pepper (if desired). Toss gently to distribute the oil.
4. Arrange sausage mixture on baking sheet in a single layer. Bake for 18 - 20 minutes, stirring after 10 minutes, until sweet potatoes are soft.
5. Garnish with green onion; serve immediately.