Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Peel the sweet potato and cut it into 1/2-inch cubes, then slice the chicken breast into bite-sized pieces.
Seed and slice the red bell pepper into strips and prepare the broccoli florets.
Place the chicken, sweet potato cubes, broccoli, and bell pepper onto the prepared sheet pan.
In a small bowl, whisk together the olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Drizzle the lemon-herb dressing over the chicken and vegetables, then toss with your hands or tongs to ensure everything is evenly coated.
Spread the mixture out into a single layer, ensuring the pieces aren't too crowded so they roast rather than steam.
Roast in the oven for 20 to 25 minutes, or until the chicken is cooked through and the sweet potatoes are fork-tender and slightly caramelized.