Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper.
In a large bowl, combine the cubed sweet potatoes, chopped red onion, and minced garlic.
Drizzle with olive oil, smoked paprika, cayenne pepper (if using), salt, and black pepper. Toss to coat evenly.
Spread the vegetables in a single layer on the prepared baking sheet.
Roast for 15 minutes.
While the vegetables are roasting, add the Italian sausage to the baking sheet with the vegetables. Break up the sausage with a spoon.
Continue roasting for another 15-20 minutes, or until the sausage is cooked through and browned, and the sweet potatoes are tender and slightly caramelized.
Stir everything together on the baking sheet before serving.
Notes
Serve hot as a complete meal or as a side dish. You can add fresh parsley or a drizzle of sriracha for extra flavor.