Place potatoes, cut side down in a large shallow roasting pan, or some facsimile. Perch bird atop potatoes. Roast for 30 minutes. Remove to baste and squeeze juice of 1/2 lemon overtop. Reduce temperature to 375 F. Roast for 60 more minutes, or until the juices of the thigh meat run clear when pricked. If bird begins to burn on top, cover loosely with a sheet of aluminum foil.