Preheat oven to 425°F (220°C). Line a rimmed baking sheet with foil and set a wire rack on top if available.
Combine ranch seasoning, garlic powder, onion powder, smoked paprika, black pepper, and salt in a small bowl. In a separate bowl, whisk together olive oil, lemon juice, and minced garlic.
Pat chicken thighs completely dry with paper towels. Brush each thigh with the oil mixture, then coat evenly with the seasoning blend, pressing gently so it adheres to the skin. Arrange skin-side up on the prepared rack.
Roast for 25–30 minutes depending on thigh size. Check at the 25-minute mark with an instant-read thermometer — the skin should be golden and the meat nearly cooked through.
Transfer thighs skin-side down into a dry, preheated oven-safe skillet over medium-high heat. Sear for 2–3 minutes until the skin is deeply golden and crackly. Do not move the chicken during searing.
Pull the chicken when the internal temperature reads 165°F (74°C) at the thickest point away from the bone. Rest for 5 minutes, then garnish with fresh parsley and serve.
