I agree with what Kurt and paramagic have said. It can be done, but it basically sucks. There is not enough ankle support in Koflachs for carving serious turns. They would work just fine for more moderate slopes that you might encounter while doing an approach. For anything much over 25 degrees or so, get the proper gear or you'll just suffer through the "experience."
I have Verticals and Fritschis, and have done the ski descents from several volcano slog summits. But it was not by any means truly fun, nor at times was it very graceful (refer to my comment about yardsaling down from Hood's icy Pearly Gates in this thread).
I'm a cheap-ass muthufugger and so I won't go dropping a wad on true randonne gear since I don't enjoy it as much as ice climbing and such. I basically bought my Fischers and Fritschis so I could approach ice climbs, not for stylin' down cinder cone summits. I've got other gear specifically for tele, which is another story...