In large bowl, toss potatoes and onion with olive oil and half of the spice/herb mixture. Spread evenly in large rimmed sheet pan.
In same bowl, toss drumsticks with remaining spice mixture. Position the drumsticks on top of the potato mixture.
Roast for 20 minutes. Remove from oven and stir potatoes. Return pan to oven and roast for an additional 10 minutes, or until an instant read thermometer inserted in the thickest part of the leg reads 165°F.
Substitute chicken thighs or roast a combination of thighs and legs.
If you don't have fresh herbs, substitute dried herbs but use half as much (1 teaspoon crushed rosemary, ½ teaspoon dried thyme).
Leftovers can be stored in the refrigerator tightly covered for two to three days.
For best results, reheat in a single layer in the oven at 350°F for ten minutes or so until they're heated through. You can also reheat in the microwave until warm. The chicken and potatoes won't be as crispy with this method, and the chicken may dry out more.