Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Dice the chicken breast and the sweet potato into uniform 1-inch cubes to ensure they cook at the same rate.
Place the chicken cubes, sweet potato cubes, broccoli florets, and sliced red onion onto the prepared baking sheet.
Drizzle the olive oil over the ingredients and sprinkle evenly with garlic powder, smoked paprika, sea salt, and black pepper.
Use your hands or tongs to toss everything together until every piece is well-coated in the oil and spice mixture.
Spread the ingredients out into a single layer, making sure not to overcrowd the pan so the vegetables roast instead of steaming.
Bake in the center of the oven for 20 to 25 minutes, or until the chicken is cooked through and the sweet potatoes are tender when pierced with a fork.
Remove from the oven and let the traybake rest for 3 minutes before serving to allow the juices in the chicken to redistribute.