Roll out pastel green fondant 1/8 in. thick; cut two 1 x 3 in. strips. Pinch ends together to form loop; fill loops with cotton and set on sides on cornstarch-dusted surface and allow to dry.
Add white fondant to orange and purple colored fondant to make pastel tones. Roll out pastel fondant 1/8 in. thick. Cut strips 1 in. x 6 in. Make ribbon roses from strips; cut to 1-1/4 in. high. Set aside.
Bake and cool 2-layer cake in 6 in. square baking pan. Stack cooled layers on foil-wrapped cake board cut to size. Prepare sides of cake for fondant by lightly icing with buttercream icing; spatula ice top of cake fluffy with buttercream.
Knead together white fondant and one yellow fondant package from primary multi pack; roll out 1/8 in. thick, and 24 x 5 in. in size. (Note: if cake is taller than 4 in., make strip 1 in. higher than cake.) Attach around sides of cake; smooth edges. Lightly curl out top edge of fondant.
Roll out remaining pastel green fondant 25 x 1in., about 1/8 in. thick. Lightly brush strip with water, attach ribbon around bottom of cake. Attach bow loops; add 1 x 2 in. “knot”. Cut fondant leaves using remaining green fondant. Position ribbon roses on top of cake; fill in with fondant leaves.