Heat oven to 450° F. In a small bowl, combine the molasses, brown sugar, 1 tablespoon of the lemon juice, and ½ teaspoon each salt and pepper.
Place the pork in a roasting pan and coat with the glaze.
Transfer the pan to oven. Roast the meat, turning it after 10 minutes, until an instant-read thermometer registers 150° F, about 10 minutes more.
Remove from oven, cover with foil, and let rest 5 minutes before slicing.
Meanwhile, in a large bowl, combine the cabbage, carrots, scallion, ginger, and hoisin sauce and the remaining 2 tablespoons lemon juice.
Layer the pork on the buns and mound the coleslaw on top.