Preheat oven to 400 degrees Fahrenheit. Line the baking sheet with parchment paper if you'd like. Slice the sausage into thick pieces on the bias.
Slice your shallots into rings.
Peel and dice your sweet potato.
Remove any out leaves from the Brussels sprouts with brown spots. Slice the Brussels sprouts in half and be sure to clean them well.
Finely chop your rosemary.
Add the sweet potatoes, Brussels sprouts, shallots, sausage, rosemary, olive oil, garlic powder (if using), salt and pepper to a large mixing bowl. Use tongs or your hands to mix well. Ensure everything is coated well in olive oil.
Arrange the ingredients on a baking sheet and transfer the pan to the oven for 15 minutes. After 15 minutes, you should see some light browning on the vegetables and sausage. Use a spatula to flip everything.
Return the pan to the oven and cook for another 15 minutes. Everything should have nicely browned edges. Remove the pan from the oven and serve!