Try using the R operator attribute .ro:
In [1]: from rpy2 import robjects
In [2]: x = robjects.IntVector(range(10))
In [3]: y = robjects.IntVector(range(10))
In [4]: x.ro-y
Out[4]:
<IntVector - Python:0x1067d3830 / R:0x102d6ef20>
[ 0, 0, 0, ..., 0, 0, 0]
In [5]: x.ro+y
Out[5]:
<IntVector - Python:0x1067d3cf8 / R:0x102d6eec8>
[ 0, 2, 4, ..., 14, 16, 18]