Preheat oven to 400°F and lightly grease a sheet pan or line with parchment paper.
In a large bowl, combine sausage pieces, bell peppers, onion, and potatoes.
Drizzle with olive oil and sprinkle with Italian seasoning, garlic powder, salt, and black pepper. Toss until everything is evenly coated.
Spread mixture in a single layer on the prepared sheet pan.
Roast for 30-35 minutes, stirring halfway through, until sausage is cooked through, potatoes are tender, and vegetables are caramelized.
Garnish with fresh parsley if desired and serve hot.