Preheat your oven to 425°F and line a rimmed baking sheet with parchment paper.
Pat the chicken thighs thoroughly dry with paper towels to ensure the skin achieves maximum crispiness.
In a small bowl, whisk together the olive oil, sea salt, black pepper, dried oregano, garlic powder, and chopped fresh rosemary.
Rub the herb and oil mixture evenly over the chicken thighs, ensuring the skin is well-coated.
Place the chicken on the prepared baking sheet and arrange thin slices of the lemon around the chicken pieces.
Roast the chicken for 20 minutes in the center of the oven.
Remove the tray and add the asparagus spears, tossing them lightly in the rendered juices from the chicken.
Return the tray to the oven and roast for an additional 10 to 15 minutes until the chicken reaches an internal temperature of 165°F and the skin is golden and crispy.