Oh, now I see my suggestion was not the right one. The rolling seems not to functiate that way. Instead it tries to calculate the shortest rolling direction to reach the next keypose. (EDIT. I think that comes from Blenders way of using quaternions instead of degrees for bone rolling, it seems to be different than with ordinary objects.)
So, what you can do: if you are rotating a bone, add keys at least every 1/4 of full roll.
I think there is no other way than rolling the animation back and forth, over and over again, so you see which way the bones go. Alt-Mousewheel is very handy for that. There is some path-illustrating tools too for bones, in the menus, but I don’t know how to use them.
EDIT. The easiest way to go in your blend-file is to delete the second diamond from your NLA-editor. Then drag the green line at about 1/3 of the original distance, you can drag it with mouse, or use the arrow keys, or scroll back and forth with Alt-Mousewheel. Activate the auto-keying from the timeline (its the red record-button you see in your scene, remember to deactivate it when done!). Then activate the “hand-icon” to get the 3D-manipulator, turn it to rotate mode, and it will take you 15 seconds to get the animation ready!