Preheat your oven to 425°F (220°C).
In a small bowl, combine lemon juice, olive oil, chopped fresh herbs, minced garlic, salt, and pepper to create a marinade.
Place the chicken breast in a shallow dish and pour half of the marinade over it, ensuring it is well coated. Let it sit for 10-15 minutes.
While the chicken marinates, peel and cut the carrot and parsnip into evenly sized sticks. Slice the red onion into thick wedges.
Toss the vegetables in the remaining marinade, making sure they are evenly coated.
On a lined baking sheet, arrange the chicken breast and vegetables in a single layer, keeping them separate for even roasting.
Place the sheet in the oven and roast for about 20-25 minutes, or until the chicken is fully cooked (internal temperature of 165°F) and the vegetables are tender and slightly crispy at the edges.
Remove from the oven and allow to rest for a few minutes before serving.
Plate your lemon herb roasted chicken alongside the crispy roasted root vegetables and enjoy your nutritious meal.