About 30 minutes before roasting, bring the chickens to room temperature. Preheat the oven to 350 degrees F. Combine the vegetable oil, 2 teaspoons salt, the white pepper, coriander and five-spice powder in a small bowl; rub all over the chickens. Tie the legs together with kitchen twine and tuck the wings under the body.
Arrange the chickens breast-side up on a rack set on a rimmed baking sheet or in a shallow roasting pan, leaving a bit of space between them. Roast until the skin is slightly golden and crisp, about 1 hour.
Make the glaze: Combine the honey, soy sauce, ginger and sesame oil in a small bowl. Increase the oven temperature to 400 degrees F. Brush the chickens all over (including the underside) with half of the glaze. Continue roasting, brushing with the remaining glaze halfway through, until the skin is deep golden brown and crisp and a thermometer inserted into the thickest part of the thigh registers 165 degrees F, about 20 more minutes.
Remove the chickens from the oven; transfer to a cutting board or platter. Pour the pan drippings into a small bowl; skim off any excess fat. Brush the chickens with the pan drippings and let rest 15 minutes. Sprinkle the chickens with the scallions and sesame seeds. Remove the twine and carve the chickens; serve with any remaining pan drippings.