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, sweet potato, carrots, and bell pepper into uniform 1-inch cubes to ensure even cooking.
In a small mixing bowl, whisk together the olive oil, lemon juice, minced garlic, dried oregano, sea salt, and black pepper.
Place the chicken cubes and all the chopped vegetables onto the prepared baking sheet.
Pour the lemon-herb dressing over the ingredients and toss thoroughly with your hands or tongs until every piece is well-coated.
Spread the mixture out into a single layer, making sure not to crowd the pan so the ingredients roast and crisp rather than steam.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken is cooked through and the vegetables are tender with golden-brown edges.
Remove from the oven and let rest for 2 minutes before serving to allow the juices to redistribute.