Be careful which ribbon you choose as they all have different properties. Wraffia is lighter weight than Wraphia and makes a softer hat, while Wraphia makes a stiffer hat. You can find some patterns around the web for crocheting with rayon raffia ribbon and paper raffia ribbon. I haven't tried any of them so can't recommend any of them.
What I have found when crocheting is that different colors of the same brand tend to work up in different ways. You'll need to experiment. So far, I have no patterns that translate to the different yarns. When you do buy a pattern, use the type of ribbon they recommend and the same color.
I had no idea others were making hats like this when I first tried them out. Everything has been an experiment. You need to rest more because the raffia ribbon requires more physical strength than wool or cotton, etc. Lately I have been using the wrist guard I got when I sprained my wrist.