How do I create a linked record in OrientDB using pyorient library

Question

I'm trying to create an entry that links to a particular class

cluster_id = -1
res = client.command('SELECT * FROM Role WHERE name="User"')
user_role = res[0]
rec = { '@Person': { 'first_name': 'joe', 'last_name': 'soap', 'username': 'soapj', 'roles':user_role._rid } }
res = client.record_create(cluster_id, rec)

But when I do this I get:

Traceback (most recent call last):
  File "project/dbtest.py", line 40, in <module>
    res = client.record_create(cluster_id, rec )
  File "/project/pyorient/orient.py", line 442, in record_create
    .prepare(args).send().fetch_response()
  File "/project/pyorient/messages/records.py", line 99, in fetch_response
    result = super( RecordCreateMessage, self ).fetch_response()
  File "/project/pyorient/messages/base.py", line 256, in fetch_response
    self._decode_all()
  File "/project/pyorient/messages/base.py", line 240, in _decode_all
    self._decode_header()
  File "/project/pyorient/messages/base.py", line 192, in _decode_header
    [ exception_message.decode( 'utf8' ) ]
pyorient.exceptions.PyOrientCommandException: java.lang.ArrayIndexOutOfBoundsException - 

However, if I instead use raw SQL it works:

res = client.command('SELECT * FROM Role WHERE name="User"')
user_role = res[0]
rec = "INSERT INTO Person SET first_name='joe', last_name='soap', username='soapj', roles=%s" % user_role._rid
res = client.command(rec)

Is there a way to do it using pyorient's native methods, or do I need to drop down into raw sql?