How to rotate all the keyframes of root bone? I found an animated character online. I want to rotate this character for all the keyframes by 180 degrees along the Z-axis. This can be done by rotating the root bone. But how do I go about rotating the root bone for all keyframes?

The animation use quaternion rotation.

Here's the .fbx file
I think the easiest way to do this - it just rotate all armature as object. To do this: 


Make sure, that you select armature in object mode. If you are in Pose mode, switch to object.
Then rotate object as you need.


Also, you can add new root bone, and parent "old root bone" to the new one. In this case you can use it to position and rotate all bones in pose mode.