Preheat the oven to 425°F (220°C). Line a large sheet pan with parchment paper or lightly grease it.
In a large bowl, toss the chicken with olive oil, garlic powder, onion powder, smoked paprika, Italian seasoning, salt, and black pepper until evenly coated.
In another bowl, toss the potatoes, broccoli, carrots, bell peppers, and onion with olive oil, salt, and pepper until coated.
Arrange the seasoned chicken in the center of the prepared sheet pan and spread the vegetables around it in a single layer.
Roast for 30–35 minutes, stirring the vegetables halfway through cooking, until the chicken reaches an internal temperature of 165°F (74°C).
For extra caramelization, broil for 2–3 minutes until the chicken and vegetables are lightly browned.
Remove from the oven and let the chicken rest for 5 minutes. Sprinkle with fresh parsley and grated Parmesan if desired.
Serve immediately with fresh lemon wedges, crusty bread, rice, quinoa, or a simple green salad.