The rolling resistance of a tyre is pretty much an anaolgy to a roller-bearing, xcept for the viscous losses unless it's raining of corse,
where the loss is very much in the hysteresis inside the tyre material itself. This phenomena takes place as the rubber and chord is continously deformed and re-deformed, as a certain amount of energy is lost in each sequence. Compare with a coil-spring being heated up when compressed and relaxed at a high frequency, like a valve-spring, that's "hysteresis".
Wiki is your friend, scroll down to "Elastic hysteresis"; http://en.wikipedia.org/wiki/Hysteresis
But in addition to that, there are all sorts of micro-movements and slippage, and as a consequence friction, between rubber and road.