Fill a frosting bag, fitted with the 2D decorating tip, with the chocolate buttercream. Pipe chocolate roses all the way around the chocolate cake layer only.
Fill another frosting bag, fitted with the 2D tip, with the strawberry buttercream. Pipe strawberry roses all the way around the strawberry layer, slightly overlapping the chocolate roses.
Fill another frosting bag, fitted with the 2D tip, with the buttercream frosting. Pipe roses all along the sides of the vanilla cake layer, and on the top of the cake.
Enjoy this amazing cake! If there are any leftovers, store them covered in the refrigerator.