The Plane rolling right meant that a/p had been trimming out a chronic and trending condition, both Right wing heavy, and NOSE HEAVY. The THS was at 3 degrees when a/p dropped, what was the nature of the dropping Nose? Was it dropping continually, and continued to drop after a/p drop? Yes, because the THS was running behind its trim command from FMC, by definition. Nose and right wing dropping, a condition identified by both the a/p and the handed-to PF. This is suggestive not of Turbulence, but controls damage, weight issues (cg), Fuel scatter, etc. or ICE. Even an inop or over limited Rudder. Perhaps?