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 broccoli and bell peppers into bite-sized pieces.
Cut the chicken breast into even 1-inch strips to ensure they cook at the same rate as the vegetables.
Place the chicken, sweet potatoes, broccoli, and peppers on the prepared sheet pan.
Drizzle with olive oil and sprinkle with oregano, garlic powder, sea salt, and black pepper.
Toss everything thoroughly with your hands or tongs until evenly coated, then spread into a single layer.
Roast for 20-25 minutes, tossing halfway through, until the chicken is cooked through and the vegetables are tender and slightly browned.
Remove from the oven and finish with a bright squeeze of fresh lemon juice before serving.