Hi,
you will need to rotate the offset vector from the rotation point to the origin of the entity.

Code:
vec_sub ( vTemp, ent.x, vRotOrigin );
vec_rotate ( vTemp, vector ( ang(angRotation - ent.pan), 0, 0 ) );
vec_add ( vTemp, vRotOrigin );
vec_set ( ent.x, vTemp );
ent.pan = angRotation;