In Splashtop 2 the option to change resolution and orientation is disabled in Windows while connected, but in Splashtop HD (the first one), it allows to change windows resolution, but it only rotates the remote screen so then it becomes a vertical windows screen while still in horizontal orientation of the tablet (completely defeating the purpose).
By the way, I am using ICS 4.0.3 and it is not rooted because currently there is no way to root my device yet (Toshiba Excite).