What is your best recipe for making buttercream roses?

I use IMBC for everything, including roses.

Of course I'm a little biased but this one has worked for me for 30 years.

http://cakecentral.com/recipes/author/indydebi

When it comes to the powder sugar and butter/crisco recipes it is more about the consistancy than having the right recipe.

You want a creamy icing that is sticky but not too soft.