Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Pat the chicken breast dry with paper towels and cut into uniform 1-inch bite-sized pieces.
In a large mixing bowl, whisk together the olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper to create the marinade.
Add the chicken pieces, broccoli florets, bell pepper strips, and sliced carrots to the bowl.
Toss everything thoroughly until the chicken and vegetables are evenly coated in the herb mixture.
Spread the mixture in a single layer on the prepared baking sheet, ensuring nothing is overcrowded so the vegetables roast rather than steam.
Place in the oven and roast for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and slightly browned.
Remove from the oven and serve immediately while hot.