Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
In a large mixing bowl, combine the chicken breast, broccoli florets, and sliced carrots.
Drizzle the olive oil and fresh lemon juice over the chicken and vegetables.
Sprinkle the dried rosemary, garlic powder, sea salt, and black pepper evenly over the mixture.
Toss everything together until the chicken and vegetables are thoroughly and evenly coated with the oil and seasonings.
Spread the mixture in a single layer on the prepared baking sheet, ensuring there is space between the pieces for even roasting.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender with golden, caramelized edges.
Remove from the oven and let the chicken rest for 5 minutes before serving to ensure it remains juicy.