By adding some yaw during a roll, it moves the roll axis. If your model rolls on the thrust line, don't mess with it. If it's off, your model will roll like someone flipping a flapjack. You might be able to see this as a yaw in the half reverse cuban eight...the model will point off course after the half roll.

Too much information: Raising or lowering ailerons can have both a differential and dihedral effect. This is good to know if you have roll coupling with rudder and you don't want to cut your wing to put in a small dihedral change.