Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Peel the sweet potato and dice it into 1/2-inch cubes, then chop the red bell pepper into bite-sized pieces.
Place the chicken breast, cubed sweet potatoes, broccoli florets, and bell peppers onto the prepared baking sheet.
Drizzle the olive oil and fresh lemon juice over the chicken and vegetables.
Evenly sprinkle the dried oregano, garlic powder, sea salt, and black pepper over all ingredients.
Use your hands or tongs to toss everything together until well-coated, then spread into a single even layer.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the sweet potatoes are fork-tender.
Remove from the oven and let the chicken rest for 5 minutes before slicing it into strips to serve alongside the roasted vegetables.