Preheat oven to 400°F.
In a baking dish, create a bed of rosemary sprigs and garlic cloves.
Place the duck legs skin-side up on top of the herbs.
Season generously with kosher salt and five spice powder on both sides.
Roast in the oven for 1 hour.
While the duck is roasting, warm the herb gravy in a small saucepan over low heat.
After 1 hour, remove duck from oven and spoon off most of the rendered duck fat.
Return duck to oven and roast for an additional 10 minutes, or until the skin is crisp and golden.
Remove duck from oven, transfer to serving plates, and spoon warm herb gravy over the top.
Serve immediately.