...it might be that the icing is a little too stiff...try adding a small amount of piping gel to the icing and see if that doesn't make a difference. It works for me!
I've read where some have added corn syrup (Karo) but I have never tried that method!
You can also add 1 tablespoon of crisco to every cup of stiff icing. The crisco will make the icing creamer, where as water would thin it down.
Another cause of ruffled edges is piping slowly and turning your nail too fast which pulls and stretchs the icing.
I had the same problem. I read somewhere to widen the narrow end of the tip, and tried that, it helped some, but every now and then I still get ragged edges. I'll have to try the Crisco thing.
I mix a small amount of piping gel in to my stiff icing. Also I find if the icing is too stiff this occurs. I make my icing stiff enough that the rose will hold it's shape but not too stiff that I am having difficulties squeezing the petals out.
why do my roses have ragged edges? This is driving me crazy!
My last class in Wilton course I is Saturday and my roses look horrible.
HELP ME PLEASE!!!!!!!!
I actually add water to my b/c icing to make it softer. Never had a problem with it. I think my roses turn out ok.
cheers
Nati
Cat,
This happened to me recently too! I tried for hours to get my roses right, and they were all jagged. I don't know why, but I never thought to check my tip, I just assumed it was the icing consistency, and kept playing around with it. Little did I know that it was the tip the whole time! the narrow end was bent into a sharp point rather than a rounded one. (you really had to look at it to see this though!) I changed tips...and viola! 
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