Prepare the oven and pan. Preheat the oven to 350°F. Grease a baking sheet or line it with parchment paper.
Rub in the margarine. Add the cubed margarine to the flour. Using your fingertips, rub the margarine into the flour, lifting the mixture as you work, until it resembles coarse crumbs.
Add the dry ingredients. Stir in the sugar, baking powder, salt, and allspice until evenly combined.
Mix the wet ingredients. In a small bowl, lightly beat the egg with the milk.
Bring the dough together. Pour the egg and milk mixture into the dry ingredients and stir until mostly combined.
Add the raisins. Fold in the raisins and gently mix just until a soft dough forms. Don't overmix.
Portion the buns. Drop heaping spoonfuls of dough onto the prepared baking sheet, leaving some room between each one. Don't smooth the dough. If using maraschino cherries, gently press half a cherry into the top of each bun.
Bake. Bake for 20 to 25 minutes, or until the rock buns are golden brown.
Cool. Transfer to a wire rack and allow to cool slightly before serving.