Preheat your oven to 425°F (220°C) 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, lemon zest, lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Rub the herb and lemon mixture all over the chicken thighs, making sure to coat the skin and the underside of the meat.
Place the chicken on the prepared baking sheet and roast for 15 minutes.
While the chicken roasts, trim the woody ends off the asparagus spears.
Add the asparagus to the baking sheet, tossing them lightly in the juices from the chicken, and place the rosemary sprig on top.
Continue roasting for another 12-15 minutes until the chicken skin is golden and the internal temperature reaches 165°F.
Let the chicken rest for 5 minutes before serving to keep the meat juicy.