Preheat oven to 350 degrees. Cook the sweet potatoes, cool and then peel. Mash up potatoes with the allspice and set aside. Slice each orange in half remove the pulp and save in a bowl. Clean out the inside of the orange shell so that it is empty, clean and ready to stuff. Add one cup of orange pulp to 2 cups of sweet potatoes mixture. Stir until blended. Stuff each orange half with sweet potato mixture leaving room on top for marshmallows. Place each orange half in a foil lined baking pan. Put marshmallows on top and bake until heated and marshmallows are toasted; about 15 to 20 minutes. It is better to do these last so they will still be warm when ready to eat.