Preheat your oven to 400°F and line a large rimmed sheet pan with parchment paper for easy cleanup.
Dice the chicken breast into 1-inch pieces and cube the sweet potato into small 1/2-inch pieces to ensure even cooking.
Place the chicken, sweet potato, broccoli florets, and sliced red bell pepper onto the prepared sheet pan.
In a small glass jar or bowl, whisk together the olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Drizzle the herb dressing over the chicken and vegetables, then use your hands or tongs to toss everything until thoroughly coated.
Spread the mixture out into a single layer, making sure the pan isn't overcrowded so the vegetables roast rather than steam.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken is cooked through and the sweet potatoes are fork-tender.
Remove from the oven and let rest for 2 minutes before serving or portioning into meal prep containers.