1 batch Italian Meringue Buttercream, Vanilla Variation, soft and ready to use
Gel coloring for roses and leaves (I used Wilton Burgundy and Moss Green)
Pastry bag and coupler
Ateco or Wilton tips #2, #8, #12, #21, #67, #101, and #104
Instructions
Position a rack in the middle of the oven. Preheat the oven to 350ºF. Coat the inside of a 13-inch × 9-inch × 2-inch cake pan with nonstick cooking spray, line the bottom with a parchment rectangle, then spray the parchment.
Prepare the batter of choice, scrape into the prepared pan and bake until a toothpick inserted into the cake shows a few moist crumbs when removed (timing will depend on the flavor selected; begin to test the cake at 20 to 25 minutes). Cool the pan on a wire rack until the cake is cool to the touch. Unmold onto a platter or a foil-covered cake base and peel off the parchment. Cool completely. The cake is ready to frost. Alternatively, double-wrap in plastic wrap; store at room temperature if assembling within 24 hours.
Smoothly frost the top and sides of the cake with vanilla buttercream. A small offset spatula is helpful in making the corners neat and smooth. Pipe a shell border on the top and bottom edges using tip #21.
Tint a larger quantity of the remaining frosting the color you want for the roses and tint a smaller amount green for leaves. The placement of the roses is up to you. Place the roses first, then the leaves (tip #67) and tendrils (tip #2) here and there if you like. Flower buds can be piped with tip #101 directly on the cake. The cake may be served immediately, or refrigerated overnight. Bring to room temperature before serving.
Recipe by Bakepedia at https://www.bakepedia.com/buttercream-roses-sheet-cake-recipe/