Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Peel and cube the sweet potato into 1/2-inch pieces and trim the woody ends off the asparagus.
In a large mixing bowl, combine the chicken thighs, sweet potato cubes, and asparagus.
Mince the garlic and finely chop the fresh rosemary and thyme.
Drizzle the olive oil over the chicken and vegetables, then sprinkle with the minced garlic, rosemary, thyme, sea salt, and black pepper.
Toss everything thoroughly to ensure an even coating of oil and herbs.
Spread the mixture onto the prepared baking sheet in a single layer, ensuring the chicken is not covered by the vegetables.
Roast for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the sweet potatoes are golden and tender.
Remove from the oven and squeeze the juice of half a lemon over the entire tray before serving.