I am having trouble with my icing. I am learning to make roses but, I guess, I can't get my icing smooth enough. I'm getting a crumbling look on the petals. I'm using the wilton recipe, thining doesn't work...Help!!

This thread includes indydebi's recipe, instructions and pictures.
http://cakecentral.com/cake-decorating-ftopict-650745.html

Debi's is really the only one that you need, but I have added a few more for you to read (just so you will know you aren't alone).

This thread recommends adding piping gel:
http://cakecentral.com/cake-decorating-ftopict-635717-bc.html+roses

Here are some threads with great information that you should review:
http://cakecentral.com/cake-decorating-ftopict-528393-bc.html+roses
http://cakecentral.com/cake-decorating-ftopict-628188-bc.html+roses
http://cakecentral.com/cake-decorating-ftopict-632010-bc.html+roses
http://cakecentral.com/cake-decorating-ftopict-638530-bc.html+roses
http://cakecentral.com/cake-decorating-ftopict-642434-bc.html+roses

Best of Luck!!!!