Prepare Crimson POM Jelly in advance of making cake. Prepare fresh pomegranate juice, if necessary.* Preheat oven to 400°F, prepare an 11 x 16 x 1/2-inch baking sheet by greasing and lining with wax paper, allow 2 inches to overhang the short end of the pan. Grease the top surface of the paper, sift together flour, baking powder, cocoa and salt; set aside, beat eggs on medium speed until fluffy and pale in color, gradually add sugar and continue beating until light and thick, about 5 minutes, add pomegranate juice, vanilla and raspberry liqueur, gently fold in the flour mixture, spread batter in prepared pan, bake in preheated oven for 8 to 10 minutes or until cake springs back when pressed with finger. Cool on wire rack for 5 minutes before assembling roll.
Combine milk and butter in a saucepan and bring to a boil, remove from heat and add chocolate; stir until chocolate is smooth and melted, add raspberry liqueur and sifted powdered sugar; beat until of spreading consistency, thin with more milk if necessary.