I think there are a couple of sets that have magister's in the title, so I'm not quite sure which set are you referring to in particular.
As for patterns on a robe, there are any number of ways to do them. For the Merciless Gladiator regalia set I did for this years blizzcon (see my gallery for pics) and did some of the details as just a fabric applique (all the gold pieces at the bottom), and some seperately as leather covered in fabric (the entire bodice, which I wouldn't recommend, as it was better in thought than in reality). You could use craft foam or leather (painted).
I would think about how you want to make the costume and what kind of designs are on it, and how you want it all to layer. I tried to look at my design in layers, figure what kind of weight and texture I wanted for each layer and then determined from that what kind of material would work best.