Several days before decorating cake, make roses using royal icing. Using the flower nail, make 25 tip 104 roses with tip 12 bases. Let dry completely. Make extras to allow for breakage.
Bake and cool 2 layer cake. Ice smooth in yellow buttercream icing. Divide cake sides into thirds. Pipe tip 2 double dot swags in white buttercream icing. Add tip 4 bead bottom border in white buttercream icing. Position roses on cake top, add tip 352 leaves in green buttercream icing.