Who needs a flower nail to decorate a cake? Watch this video to learn how to pipe buttercream roses directly onto a cake! How to Decorate a cake with buttercream roses Â« Cake Please note: You are currently browsing img simple and stunning cake decorating techniques girl that is 680x1020px in size. This image is listed in rose cake ideas category. How to Decorate a cake with buttercream roses Cake, 680x1020 in 93.87 KB.