Preheat your oven to 400°F (200°C) and line a large rimmed sheet pan with parchment paper for easy cleanup.
Cut the chicken breast into 1-inch cubes and dice the sweet potato, broccoli, and bell pepper into uniform, bite-sized pieces.
In a small bowl or jar, whisk together the olive oil, lemon juice, oregano, garlic powder, sea salt, and black pepper until well combined.
Place the chicken and all the vegetables onto the prepared sheet pan and drizzle the lemon-herb dressing over the top.
Toss everything together with your hands or tongs until every piece is thoroughly coated in the oil and spices.
Spread the mixture into a single even layer, ensuring the chicken and vegetables are not crowded so they roast beautifully.
Bake for 20 to 22 minutes, or until the chicken is cooked through and the sweet potatoes are fork-tender and slightly caramelized.