Preheat oven to 450ºF. Line bottom and sides of a 9-by-13-inch baking pan with heavy-duty aluminum foil. In baking pan, toss potatoes and shallots with oil, rosemary and 1/2 tsp. salt. Roast for 15 to 20 minutes.
In a small bowl, combine soy sauce, honey and mustard. Remove baking dish from oven and stir potato mixture. Mist a wire rack with cooking spray and place it on top of baking dish.
Place chicken on rack. Brush with soy sauce mixture and roast until an instant-read thermometer registers 165ºF when stuck into thickest part of thigh, about 35 minutes (check chicken after 20 minutes; if skin is browning too quickly, tent chicken with foil). Let rest 5 minutes. Serve chicken with potato mixture.