Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Trim and halve the Brussels sprouts, peel and slice the carrot into half-inch rounds, and cut the red onion into thick wedges.
Finely mince the garlic clove and strip the leaves from the rosemary and thyme sprigs, chopping them finely.
In a large mixing bowl, combine the chicken breast, prepared vegetables, olive oil, minced garlic, herbs, sea salt, and black pepper.
Toss everything thoroughly until the chicken and vegetables are evenly coated in the oil and herb mixture.
Spread the ingredients in a single layer on the prepared baking sheet, ensuring they are not overcrowded to allow for proper browning.
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 charred edges.
Remove from the oven and let the chicken rest for 5 minutes before slicing to keep it juicy.
Serve the sliced chicken alongside the roasted vegetables while warm.