In reply to 19G:
I'd value a guess that roped soloing is used mostly on big walls (aid climbing), and the with the easiest access and amount of lines being in US... well, I agree with ya.
Roped solo free climbing is much less popular, mostly because you'd need to either climb or jug each pitch twice and that's time consuming while free climbing. So I'd guess that this is mostly done on single pitch places (where one can easily rap down and clean, before venturing up another line).
Soloing, where you occationally rope solo/belay portions (back looping) often require fixed protection so you don't need to clean them. Well, I know people climb like that in the Alps and Patagonia... Most likely in the states as well.
So I guess it depends, on what you mean by roped soloing
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