Rinse and pat dry your drumsticks. Combine lemon juice, zest, rosemary, olive oil, garlic, salt and pepper in a bowl; mix well. Add drumsticks to the mixture and let marinate for 20-30 minutes. Preheat oven to 400°F. Heat a heavy drizzle of oil on the stove in an oven safe skillet. When oil is hot sear both sides of the drumsticks making sure that they are not too close to one another. Place in the oven and roast for 30 minutes or until internal temperature reaches 165°F. Finish with a squirt of lemon juice as you remove it from the oven.