According to this page: https://en.bitcoin.it/wiki/Poolservers bitcoind's rollntime support is 'Supported, but not advertised'. I am taking that to mean that it doesn't provide the X-Roll-NTime header that would advertise this support, but you can increment the ntime value to get extra nonce space and still submit found blocks after doing this.
Is this correct? If so, what would be the max amount that a mining client can increment the ntime value?