I did this wedding cake for a couple in our church this past weekend. This one just about finished me off!! It sure looks pretty though.
The cake the bride showed me, the one I used as a model, was covered with fondant. But since cost was an issue, we went with buttercream. When you're using fondant on fondant, it sticks better, especially when the add-ons are heavier, like roses. So to make sure they didn't fall off, I left the roses on the toothpicks that I formed them on, and just stuck them into the cake. It worked well.
I made the roses and leaves three or four days ahead of when I needed them, so they could harden. I also added Gum Tex to the fondant to make it more workable and so it would dry quicker.
I purchased velvet ribbon instead of using fondant. Fondant ribbon looses it's shape so easily, and I didn't need the added stress! And, once again I cheated with craft foam - I made the swags out if when I started having issues with the fondant.
The design, with the smaller tier being underneath larger tier, created havoc with my normal support system, so I had to improvise to overcome that as well.
The figurine on top in the first picture was provided by the bride. It was too tall and heavy and actually make the cake top-heavy, so I didn't put it on until the bride and groom were taking pictures and cutting the cake. I was afraid it would fall. I would have chosen a smaller topper, possibly even spray painting it black - wouldn't that have looked cool?
Anyway, congrats, Rachel and Brad!