Update basic.py

theano/tensor/basic.py

@@ -4220,10 +4220,7 @@ def roll(x, shift, axis=None):
             axis = 0
 
     if axis < 0:
-        if x.ndim == 0:
-            axis = 0
-        else:
-            axis = axis % x.ndim
+        axis += x.ndim
 
     # Shift may be larger than the size of the axis. If so, since the
     # roll operation is cyclic, we can take the shift modulo the size