1. Preheat your oven to 400 F (200 C). Line a large baking sheet with parchment paper or aluminum foil for easy cleanup.

2. Wash and chop all your vegetables. Cut the broccoli into small, uniform florets, and slice the bell peppers and red onion into roughly 1-inch pieces. Slice the pre-cooked chicken sausage into 1/2-inch rounds. Aim for similar sizes so everything cooks evenly.

3. In a large mixing bowl, combine the chopped broccoli, bell peppers, red onion, and sliced chicken sausage.

4. Drizzle the olive oil over the ingredients in the bowl. Sprinkle with Italian seasoning, garlic powder, salt, and black pepper. Toss everything gently with your hands or a large spoon until all the vegetables and sausage are lightly coated with oil and seasonings.

5. Spread the seasoned chicken sausage and vegetables in a single layer on the prepared baking sheet. Do not overcrowd the pan; if necessary, use two baking sheets to ensure everything roasts rather than steams.

6. Place the baking sheet in the preheated oven and roast for 20-25 minutes. About halfway through cooking (around the 10-12 minute mark), give the ingredients a good stir or flip them with a spatula to ensure even browning. The vegetables should be tender-crisp, and the sausage should be nicely browned and slightly caramelized when done.

7. Once cooked, remove the sheet pan from the oven. If desired, sprinkle with fresh chopped parsley for a pop of color and freshness. Serve hot and enjoy your healthy and flavorful meal!