Heat oven to 400°. Lightly coat a roasting pan and rack with cooking spray. Combine rosemary, garlic and salt in a bowl. Remove giblets and neck from chicken and trim off all visible fat. Starting at the neck cavity, gently loosen skin from breasts and drumsticks; spread rosemary mixture evenly under skin. Tuck wing tips under back of chicken; tie ends of drumsticks together with twine. Season with additional salt and black pepper to taste; place breast side up in pan. Roast, basting twice with pan juices, until a meat thermometer inserted into thickest part of thigh (and not touching bone) reads 175°, about 1¾ hours. Let stand 10 minutes before carving. Garnish with rosemary sprigs and lemon slices, if desired, and serve.