You can't rotate a special effect, unless it would be a model.
To do this you should create a unit which has the model of the special effect, and then you can turn it.
Use dummy unit that looks like a special effect, I tried it but I don't understand how so I start using Special Effect... Can you write me the trigger??
I guess u mean the Max. Pitch and Max. Roll of a unit. ( dont know the exact name in the editor )
e.g. a footman has "10" and
To change the value hold shift and doubleklick / press enter
( -90 degree would be that what you u want )
Well.First of all if you wanna rotate a special effect make a Unit with the model u want.Then if you wanna attach it use triggers.
special effect-Add special effect to unit.