Pour liquid into bowl of stand mixer with flat beater attached. Add mashed potatoes (don't worry if a few small lumps remain), shortening, salt, eggs and milk, creaming thoroughly.
Mix in two cups flour.
Change to dough hook and work in as much of remaining flour as possible.
Place in greased bowl away from drafts and let rise until double.
Punch dough down, then shape into your choice of roll shapes, leaving unused dough in sealed bowl for later use. If I make the full recipe, it makes a very full lasagna pan of rolls. Be sure to grease the pan using butter or margarine; it makes removing the rolls easy and adds flavor to the crust.
Let shaped rolls rise for approximately one hour, then bake at 350° until golden brown and lightly browned on the bottom. Timing will depend on size and shape of rolls.
Once rolls are baked and removed from oven, brush with melted butter (or unwrap part of a stick of butter or margarine and rub it along the tops of the rolls).