Preheat your oven to 400°F (200°C).
Peel and chop the carrots and parsnips into 1-inch chunks, and halve the Brussels sprouts.
Mince the garlic cloves and whisk them together in a small bowl with the olive oil, rosemary, thyme, sea salt, and black pepper.
Place the chopped vegetables on a large parchment-lined sheet pan and toss with half of the herb oil mixture until well coated.
Rub the remaining herb oil mixture evenly over the chicken breast.
Heat an oven-safe skillet over medium-high heat and sear the chicken for 2-3 minutes per side until a golden crust forms.
Transfer the chicken to the sheet pan, nestling it among the vegetables.
Roast in the oven for 18-22 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and browned.
Remove from the oven and let the chicken rest for 5 minutes before slicing to keep it juicy.