Preheat oven to 350ºF. Spray a 15 " x 1" baking pan with cooking spray. Line with waxed paper and grease again. Set aside.
Combine flour, cocoa, baking powder and salt in a small bowl. Set aside.
In a large bowl beat eggs on high for 3 minutes. Gradually add sugar, beating until it becomes thick and lemon-coloured. Beat in food colouring, buttermilk, oil, vinegar and vanilla.
Fold flour mixture into eggs mixture. Spread into prepared pan.
Bake for 10-15 minutes, making sure not to overcook. Cool for 5 minutes.
Spread out a kitchen towel and dust with confectioner's sugar. Invert the cake on to the prepared towel. Peel off the waxed paper and GENTLY roll up the cake like a jelly-roll. Let cool completely.
Prepare frosting (see below). Unroll cake; spread filling over cake to withing 1/2 inch of edges. Sprinkle with raspberries;spread our evenly. Roll up again. Place seam down on a serving dish and dust with additional confectioner's sugar. Refrigerate for 1 hour. Keeps well for 24-48 hours.