ventus45, your cross control theory is intriguing.
(Wouldn't the pilots feel the yaw displacement as well as the roll if the rudder was out when the ap went off? It should be in a trimmed position up until the AP goes off, so quite possibly no kick and no roll). What could happen, however, is that as the aircraft changed speeds, the rudder may not be in correct position for the new airspeeds. If you aren't on the pedals, a yaw/roll moment could develop if the aircraft isn't trimming or finding new positions for the rudder by itself.
To that one can factor int a case of mild vertigo for PF, a pilot used to the incredibly smooth balanced flight modern airliners are capable of providing.
The RLU position may not be so hard to explain:
by the time the controls were passed, it is likely that the (originally PNF) now in control pilot used both hands and feet to try to recover, so it's hard to say if the Rudder was displaced many times before impact, or perhaps stuck on high and remained stuck. With the THS remained stuck ... it can lead one to a symmertrical line of inquiry.