How long does it take for butter cream roses to dry so they won't crush when I try to pick them up?

If you let them air dry for a few hours you will will be able to pick them up (very carefully). If I have a lot of roses to do- I like to do them a few days ahead of time to give the color time to cure and give them additional time to crust.

Put them in the freezer and you will be able to use them in about 15 min.

HEre is a thread with add'l info on BC roses, including a more detailed explanation of why air drying works well, and the caution needed when working with frozen icing roses: http://cakecentral.com/cake-decorating-ftopict-676696-air.html