greetings porcus protected attributes of a class are only available to methods of the class, methods of classes based on that class, or methods of friends of the class. this means that any methods of ISceneNode can access RelativeRotation just fine but if i tried to access it directly in my wrapper there would be a compile error.
given that, there are methods you can use to access these protected properties:
ISceneNode.getRotation() => returns RelativeRotation
ISceneNode.setRotation() => sets RelativeRotation
ISceneNode.getScale() => returns RelativeScale
ISceneNode.setScale() => sets RelativeScale
ISceneNode.getPosition() => returns RelativeTranslation
ISceneNode.setPosition() => sets RelativeTranslation
ISceneNode.setAutomaticCulling() => returns AutomaticCullingState
ISceneNode.getAutomaticCulling() => sets AutomaticCullingState
these will give you full access to the metioned properties. the same style is used throughout Irrlicht so if you see some properties you would like access to and they are protected, seek out some public methods that access them using the Irrlicht manual. if you cant find any this usually means the designers of the class meant for that attribute to be hidden for some reason.