Preheat oven to 375°F. Line a large sided baking sheet with parchment paper. Place the first 8 ingredients in a medium bowl and toss to coat.
Set the chicken legs on the baking sheet, skin side up. Set the rosemary sprigs, lemon slices and potato mixture around the chicken. Drizzle any liquid left in the bowl that held the potatoes over the chicken.
Roast the chicken, basting with pan juices occasionally, for 50 to 55 minutes, or until the chicken is cooked through and the potatoes are tender.
Recipe Options: Instead of chicken legs, use four bone-in chicken breasts in this recipe.