Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Peel the sweet potato, carrots, and parsnips, then dice them into uniform 1-inch cubes to ensure even cooking.
In a small bowl, whisk together the olive oil, lemon juice, lemon zest, minced garlic, dried rosemary, dried thyme, sea salt, and black pepper.
Place the chicken breast and diced root vegetables on the prepared baking sheet, then drizzle the lemon-herb mixture over everything.
Toss the vegetables and coat the chicken thoroughly with your hands or tongs to ensure every piece is seasoned.
Spread the ingredients out in a single layer, ensuring the chicken has space around it to roast properly.
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 fork-tender and golden brown.
Let the chicken rest for 5 minutes before slicing to keep it juicy, then serve alongside the roasted vegetables.