NumPad0=set playercontroller bZeroRoll False | set playercontroller rotation (pitch=0,yaw=0,roll=16384)
NumPad1=set playercontroller bZeroRoll False | set playercontroller rotation (pitch=0,yaw=32768,roll=-16384)
NumPad2=set playercontroller bZeroRoll False | set playercontroller rotation (pitch=0,yaw=16384,roll=32768)
NumPad3=set playercontroller bZeroRoll False | set playercontroller rotation (pitch=0,yaw=-16384,roll=0)
NumPad4=set playercontroller bZeroRoll False | set playercontroller rotation (pitch=16384,yaw=0,roll=16384)
NumPad5=set playercontroller bZeroRoll False | set playercontroller rotation (pitch=-16384,yaw=0,roll=16384)
NumPad6=set playercontroller bZeroRoll True | set playercontroller rotation (pitch=0,yaw=0,roll=0)
This article over at leveldesigner has all the gory details:
http://www.leveldesigner.com/index.php?action=doc&ID=168