Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Cut the chicken breast and the peeled sweet potato into uniform 1-inch cubes to ensure even cooking.
In a large mixing bowl, whisk together the olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Add the chicken cubes, diced sweet potatoes, broccoli florets, and sliced red bell peppers to the bowl and toss thoroughly until everything is well-coated in the herb oil.
Spread the mixture in a single layer onto the prepared baking sheet, ensuring the pieces aren't overcrowded so they roast rather than steam.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken is cooked through and the sweet potatoes are fork-tender.
Remove from the oven and let rest for 2 minutes before serving to allow the juices to redistribute.