To make ADDED object have preset rotation
With [ LOGIC BRICKS ]
You would have to make the object that is spawning objects have a PREDEFINED rotation.
(You can do this by making an ANIMATION with a single key-frame of the desired rotation)
P.S I think you can also alternately use the CONSTRAINT logic brick ( not sure)
With [ PYTHON ]
Put this script on the object that is spawning objects.
(This isn’t the best way in PYTHON, but is the best I could do on short-notice)
from bge import *
#Put the name of the added object here.
OBJECT = ""
#Put here the desired ROTATION_DEGREE here.
ROTATION = 90
#You can have as many ROTATION_PRESETS as you want. You just need to create them.
SPAWNED_OBJECT = logic.getCurrentScene().object(OBJECT, cont.owner)
[ AFTER THOUGHS ]
Hope it helps