Converted 'Roll' parameter to degrees.

src/MultitouchInteractor.py

 import vtk
+from math import degrees
 from threading import Thread
 
 from objreader import read_obj
@@ -42,7 +43,7 @@ class MultitouchInteractor():
         self.camera = camera
 
     def on_rotate(self, event):
-        self.camera.Roll(event.angle)
+        self.camera.Roll(degrees(event.angle))
 
     def on_pinch(self, event):
         pass