Preheat the oven to 400 degrees F; spray the rack of a roasting pan with nonstick cooking spray. Remove the chicken giblets and neck from body cavity; refrigerate or freeze for another use. Rinse the chicken under cold running water inside and out; pat dry with paper towels.
Place the lemon, onion, rosemary, thyme, and garlic in the body cavity. Place the chicken, breast-side up, on the rack in the roasting pan. Roast 30 minutes; pour the broth and lemon juice over the chicken. Reduce the oven temperature to 325 degrees F. Roast, basting frequently, until cooked through and the juices run clear when the thigh is pierced in the thickest part with a fork, about 1 hour longer. Transfer the chicken to a cutting board, let stand 15 minutes.
Meanwhile, pour the pan juices into a medium saucepan, skimming off any fat and reserving 1 tablespoon of the juices in a small bowl. Dissolve the cornstarch in the reserved juices. Add the wine, scallion, sage, and 1/4 cup water to the saucepan; bring to a boil and boil 5 minutes. Reduce the heat to low and whisk in the the dissolved cornstarch; cook, stirring constantly, until the gravy thickens, about 1 minute. Carve the chicken and serve with gravy. Remove the skin before eating.