Well let's just say I tried to make my Buttercream roses cascade down the side of my MIL and FIL anniversary cake last year and they just slid! Everytime I moved them they kept sliding down so I just kept them on the edges of the second tier and along the border and piped leaves overtop to hide where they had slid.Not much help! Sorry!
I read in another part of the forum where someone took toothpicks and used them to afix the roses to the side of the cake. Just be sure to let whomever know that there are toothpicks holding them on. And also, to let the roses harden a little before attaching them, less likely to fall that way.
That's a great idea!! Where was that idea last year when I tried to stick flowers on a cake!HA!HA!
I use toothpicks in mine ... I push them through the center of the rose.. I make my roses on the dowel stick as they're lighter and easier to get them to stay on the sides of the cake than the rose made on a flower nail. In the tutorial on making roses on a dowel stick, it shows you how to get the roses to stay on the side of the cake w/a toothpick 
Cheryl,
Is that tutorial in the Article section??
Does the toothpick trick work if the flowers are buttercream or do they need to be royal icing?
Here is a link to the article:
http://www.cakecentral.com/article50-Making-Buttercream-Roses-on-a-Stick.html
There are some photos on how to attach your roses to the side of your cake using toothpicks. Scroll down to Step 7.
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