I had been using the bench scraper (dipped in hot water & then dried) method of smoothing my buttercreams. And this method works ok, I just hate dipping and wiping, dipping and wiping, on and on and on. I have a 12 x 12 square Spiderman cake due tomorrow and thought I'd try your method, since my bench scraper is only 6" wide. OMG!!!!! I LOVE this method! I used Indydebi's buttercream recipe, did a crumb coat, waited a few minutes, applied the final coat and waited about 10 minutes to be sure it was fully crusted. I COULD NOT believe my eyes as I watched the roller smooth ALL the little air holes, bumps & such. This cake looks SO smooth, I almost hate to add anything to it!! Alas, I must go add boarders and spidey's head. I'll post a picture a little later tonight.
I am with you 100%. I don't know how I ever made it without my roller!