Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Trim the ends off the Brussels sprouts and halve them; peel the carrots and slice them into 1/2-inch thick rounds.
Cut the chicken breast into 1-inch bite-sized pieces to ensure they cook evenly alongside the vegetables.
In a small bowl, whisk together the extra virgin olive oil, lemon juice, lemon zest, dried oregano, garlic powder, sea salt, and black pepper.
Place the chicken, Brussels sprouts, and carrots on the prepared baking sheet, then pour the lemon-herb mixture over the top.
Toss everything thoroughly with your hands or tongs until well-coated, then spread into a single layer so nothing is crowded.
Roast for 20-25 minutes, tossing halfway through, until the chicken is cooked through and the vegetables are golden and tender.