Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Dice the sweet potato into 1/2-inch cubes and chop the red bell pepper into bite-sized pieces.
Cut the chicken breast into even 1-inch chunks to ensure they cook at the same rate as the vegetables.
In a large mixing bowl, whisk together the olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Add the chicken, sweet potato cubes, broccoli florets, and bell peppers to the bowl, tossing thoroughly until everything is evenly coated in the herb marinade.
Spread the mixture in a single layer on the prepared sheet pan, ensuring nothing is overcrowded so the veggies roast rather than steam.
Roast for 20-25 minutes, tossing halfway through, until the chicken is cooked through and the sweet potatoes are tender and golden.
Remove from the oven and finish with an extra squeeze of fresh lemon if desired before serving.