Can anyone suggest a way to form ruffles like these? 

The pic is very washed out - hard to make out the details but it looks to me like very thinnly rolled fondant cut into triangles (or maybe even squares) and folded (rolled?)  into shape.  I'd guess at least 2 or 3 layers.

I think kakeladi is correct, but I would probably use gum  paste, since it is stronger. I would guess it to be more like six or seven different folds.  Add tylose to the fondant for strength and allow to dry, supported in the appropriate shape, before applying with melted chocolate or RI.

Looks like wafer paper to me. Easier to get the firm rolls.

I can't do anything with wafer paper.  If I tried to curl it like this it would just break.  This looks too thick for wafer paper, to me, but I could be wrong.

Yeah I doubt it's wafer paper.  Tylose/fondant rolled thin is still my guess :)