This is only our 3rd time using the rolled buttercream. 1st time went great but last time and this time arent going well. We keep getting lots of cracking. On the one cake we can still see the cake through so we did the next one thicker but its causing more cracking. We've tried the rubbing more powdered sugar on it, but its just not looking like its going to smooth out. Any suggesstions?

If it is cracking then either the mixture is too dry, or it hasn't been mixed enough, or it is drying before it gets onto the cake ..

Just checking: Are you sure that you mean "rolled Buttercream" and not "rolled Fondant"?

"rolled Buttercream" = shortening, corn syrup, flavoring and powdered sugar

or

"rolled Fondant" = gelatin, water, glucose syrup, glycerin, and powdered sugar

I am going to try the marshmallow rolled buttercream recipe on here today, fingers crossed!

I added a tsp of water to my rolled buttercream because it was really grainy. It helped dissolve the sugar a little and I kneaded it for a while to make it smoother.