UPDATE 3/3: Ryan Seacrest just said Rob will be on at around 7am PST. Listen now! or on your iheartradio app. Follow us on twitter for the very latest - we will post the clip when it's available.
Fellow fansite Let Me Sign has the details, after they say they heard Ryan announce this morning he'd be interviewing Rob tomorrow! - We assume he will be talking Water for Elephants since a new clip will air during American Idol. Later, the official Water for Elephants Facebook page confirmed the news.
We'll keep you posted. As far as we know, the last time Rob talked to Ryan was at the New Moon premiere. You may remember things ended on an awkward note (see video below). So it should be interesting to see how the interview goes.