I think there is no need to roll (or change transform orientation) any single bone in Blender.
Just create armature, then use "Child of" etc to rotate it along X+.
Another problem is:
During the transition from initial anim to a walk anim ('testmodel name' -> 'testanim walk') the custom model 'falls' through the floor. On the original model this transition occurs smoothly (linearly) in this case (pic.1).
Looks like the 'origin' bone has an offset in walk anim, but it's not (pic.2).
Why this is happens?
Thanks.
******************* update ******************
The custom model also falls through the floor whet it spawns (pic 3).
Hmm...