In advance make roses. Use tip 12 base and tip 104 to make 14 pink royal icing roses. Use tip 12 base and tip 103 to make 14 pink royal icing roses. Let dry.
Bake and cool 2-layer cake.
Ice smooth with pink buttercream icing.
Mark cake for scallops above roses, mark 1 in. up alternating 1-7/8 in. wide and 1-1/4 in. wide. Center high point of scallops. Shorter scallop is 2-1/4 in. from top edge of cake. Wider scallop is 2 in. from top edge of cake. Pipe tip 3 pink balls on scallop marks.
Pipe tip 21 shell bottom border in pink.
Attach two sizes of roses under scallops. Pipe tip 352 leaves in green. Divide top of cake into 10ths, 2 in. from edge of cake. Make scallop 1 in. deep and pipe with tip 3 balls in pink. Mound 7 roses on top center of cake and add tip 352 green leaves.