Preheat your oven to 425°F (220°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Pat the chicken thighs completely dry with paper towels; removing moisture is the secret to achieving that perfectly crispy skin.
In a small ramekin, whisk together the dried rosemary, dried thyme, garlic powder, sea salt, and black pepper.
Drizzle half of the olive oil over the chicken thighs and rub the herb mixture evenly over the skin and the underside of the meat.
Place the chicken thighs on the prepared baking sheet and roast in the center of the oven for 15 minutes.
While the chicken starts roasting, trim the woody ends off the asparagus and toss the spears with the remaining olive oil and a pinch of salt.
Remove the baking sheet from the oven, add the asparagus and the lemon (cut into thin rounds) around the chicken, then return to the oven.
Roast for another 15 to 20 minutes until the chicken reaches an internal temperature of 165°F and the skin is golden brown.
Let the chicken rest for 5 minutes before serving to allow the juices to redistribute for a moist and tender result.