Several days in advance: Make royal icing roses and attach to wires. Let dry. Also: Using royal icing, make 40 tip 352 leaves on wires and 100 tip 225 drop flowers with tip 2 dot centers. Let dry.
And: Prepare base board. Cut out board shape 1 in. larger on all sides than largest pan. Cover with rolled fondant.
Bake and cool 2-layer cakes (bake two 1 1/2 in. high layers for 3 in. high cakes). Prepare for Stacked Construction. Ice smooth.
Attach drop flowers to cake sides with icing dots. Pipe tip 4 bead bottom borders. Prepare rose sprays. For top tier, gather 4 tip 101, 1 tip 103 and 2 tip 104 roses with 6 leaves; secure with florist tape. Gather 2 tip 124, 1 tip 103 and 2 tip 101 roses with 6 leaves; secure with florist tape. Tape 2 groups together and arrange in Flower Spike, securing with extra fondant if needed. Repeat for 2 additional sprays, increasing number of flowers and size for each tier.
At reception: Insert flower spikes. Cut drinking straws to 3 in.; insert cake pick into straws, then insert into cake top.