Preheat the oven to 450 F.
Pat the chicken legs completely dry with paper towel. This is what lets the skin crisp.
In a large bowl, combine the olive oil, lemon juice, chopped garlic, rosemary, salt and pepper.
Add the chicken and turn until every piece is coated.
Arrange the legs skin side up on an oiled baking tray, leaving space between them so they roast rather than steam.
Dot the butter over the chicken.
Roast for about 40 minutes, until the skin is golden and the juices run clear.
Spoon the pan juices over the chicken and serve.
