In advance: Make roses. Tint royal icing rose. Using Flower Nail covered with small waxed paper square, make 30 Tip 124 roses with Tip 12 bases. Make extras to allow for breakage. Let dry at least 24 hours.
Bake and cool two 1-layer cakes; freeze for easier cutting. Cut using the 2 1/2 in. round cutter from set. Place cake circles on cooling grid placed over cake pan or cookie sheet.
Melt Candy Melts following package instructions. Pour over cakes to cover; let set.
Tint small amount of buttercream icing green. Attach roses to cake tops using a dot of icing. Pipe tip 352 leaves. Position cakes on cake stand.