You can rotate GoDrawing objects in GoDiagram.
GoDrawing f = new GoDrawing(GoFigure.Spade);
f.Angle = 30;
And the downloadable sample in this forum entry has a rotatable text object and shows some rotation UI:
(see Need to build a Theater seating diagram)
But, in general, GoDiagram doesn’t have rotatable nodes. And it’s unlikely to ever get them. But the good news is that both GoXam and GoJS do.