I’ve tried rigify Blender 2.77 with and without a root bone, and it works. I believe there will be a root (empty) urgency for doing any root animations.
I do figured out, that we can export all animations as NLA’s with the fbx (as binary), be sure that there is no aktive Action before export. “But the naming of all fbx-implemented animations will start with the Name of the mesh. And this make it hard to find the right name in the stack.”
Also i can ex/import a **rigify **rig as it is (check deform bones only). No need to change from blender Units to metric system.