Normally, the picture lags audio. Is your picture leading the audio? If so, you'll need to find a way to delay the video.

Experiment a little. I'm not familiar with the xbr. How is lip sync for an analog TV output. As a test you could use headphones or an A/V receiver hookup. If lip sync is better with analog output, you could use a converter. Another approach might be to go directly from ROKU to PLAYBAR.

Do you also have a cable box or disc player connected to the TV? How is lip sync here?