Bake and cool 2-layer heart-shaped cake. Stack cake layers on foil-wrapped cake board using buttercream icing as filling.
Spatula ice smooth with buttercream icing. Tint a portion of fondant light rose. Roll out light rose fondant 1/8 in. thick; cut two 1 x 15 in. long strips. Position strips flat around top border of cake; trim to fit heart shape.
Tint portion of fondant dark rose. Make 19 ruffled ribbon roses; attach flowers to top edge of cake with damp brush. Tint small portion of fondant light green; roll out 1/8 in. thick; cut 20 leaves using smallest Cut-Out. If desired, place leaves on thin foam and score vein lines with veining tool. Attach with damp brush.
Roll out remaining light rose fondant 1/8 in. thick. Cut ¼ in. wide strips; position on cake top to form message. Roll ½ in. balls of white fondant and attach to bottom border with buttercream.