Preheat oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Dice the sweet potato into 1/2-inch cubes and chop the bell pepper, red onion, and broccoli into bite-sized pieces.
Slice the chicken breast into even 1-inch strips to ensure quick and even cooking.
In a large bowl, whisk together the olive oil, lemon juice, oregano, garlic powder, salt, and pepper.
Add the chicken and all the vegetables to the bowl, tossing thoroughly until everything is evenly coated in the herb marinade.
Spread the mixture in a single layer on the prepared baking sheet, ensuring nothing is overcrowded.
Roast for 20-25 minutes, tossing halfway through, until the chicken is cooked through and the vegetables are golden and tender.