in general, wood ashes are ok around roses as they supply some nutrients that promote flowering. Howver, if you plan on dumping a large quantity right around the root system,you might want to reconsider the dumping location as too much wood ash might make the soil more alkaline than most roses prefer.

ohvgal

You might find these two links helpful. One link is so long I had to post it as a clickable. :)

http://www.hort.uconn.edu/ipm/homegrnd/htms/woodshes.htm

Newt

Here is a link that might be useful: wood ash in the garden