Garlic and Citrus Roasted Chicken

(5 to 6-pound) whole roasting chicken, neck and giblets discarded

Salt and freshly ground black pepper

orange, quartered

lemon, quartered

head garlic, halved crosswise, plus 3 garlic cloves, chopped

reduced-sodium chicken broth

frozen orange juice concentrate, thawed

fresh lemon juice

olive oil

chopped fresh oregano leaves

Kitchen string or butcher twine