I am using PlaceNodes to mark locations on earth maps. I would like to rotate the PlaceNodes so they point in specific directions (flat 2D images but rotated around the center point of the image). The PlaceNodes contain an osg::Image, which has alignment set to ALIGN_CENTER_CENTER. I am able to scale them using the following code:
Maybe you need to use text-geographic-course like illustrated in annotation.earth exemple (possible also through code, in textSymbol).
Like said by Glenn it will be an "on screen" rotation, but it will be automatically computed at each frame to follow a given bearing.