If you can buy it - try using the Wilton decorator icing in the tub from the craft store. I had a terrible time with roses until I had to buy it one time. That stuff worked great! I also use a hershey kiss for the base!
~Chelle
Hi Dorothy,
If you're roses are laying over it sounds like your buttercream is too soft. You BC needs to be stiff consistency and a good way that my Wilton instructor showed me was that a spoon should stand upright in your icing.
The video below really helped me when I first started making roses.
http://www.wilton.com/decorating/basic/rose_video_56.cfm
Best regards,
Christina
I'm not sure about your icing consistency - that shouldn't be happening if you are using thick consistency. I use pretty much medium with piping gel mixed in otherwise I get jagged edges on mine.
As Chelle already mentioned - using Hershey kisses as the base is great! I just did that again last night. I just seem to hate filling a second bag and switching back and forth to use a frosting base. Plus I don't get that problem of the base sort of flopping over as I make petals. And I like the little surprise of chocolate in the middle of the roses. 
I also read on here that some freeze the base to get it hard so they don't worry about it moving when they are doing the petals=) Jen
Ps..I would go for the hershey kiss though...Yummy suprise!
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