Preheat your oven to 425°F (220°C) and line a sheet pan with parchment paper or lightly grease it.
Prepare the chicken by patting it dry. Season both sides with salt, pepper, and a drizzle of fresh lemon juice.
Peel and cut the carrot and parsnip into uniform sticks or rounds. Slice the red onion into wedges.
Toss the vegetables in a bowl with olive oil, a little salt, pepper, and roughly chopped rosemary and thyme.
Arrange the chicken breast and vegetables on the sheet pan, placing the chicken in the center and the vegetables around it in a single layer.
Squeeze additional lemon juice over the chicken and vegetables and garnish with the remaining whole sprigs of rosemary and thyme.
Roast in the preheated oven for approximately 20-25 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the vegetables are tender and slightly caramelized.
Once done, remove from the oven, let rest for a few minutes, and serve warm.