Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Cut the chicken breast, sweet potato, and red bell pepper into uniform 1-inch cubes to ensure even cooking.
Break the broccoli into small, bite-sized florets and place them in a large mixing bowl with the other chopped ingredients.
In a small jar or bowl, whisk together the olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Pour the lemon-herb dressing over the chicken and vegetables, tossing thoroughly until every piece is well-coated.
Spread the mixture in a single layer on the prepared baking sheet, making sure not to overcrowd the pan.
Roast for 20 to 25 minutes, tossing halfway through, until the chicken is cooked through and the sweet potatoes are golden and tender.