The only attributes for the root joint put in keyframes are the animations like idle, move, attack etc. Those you need to have as a keyframe on root as well.
For example: Your joint "Turret" has a rotation from frame 10 to 40 which you want for your turret to turn. The way for the exporter to know that these 30 keys are the animation for turning is to put this information on the root joint. From frame 10 to 40 you need to have this attribute assigned to the root joint.
This way you have two joints, Turret and root, Turret is parented to root. root has a keyframe with the attribute idle from frame 10 to 40, Turret has the rotational animation from frame 10 to 40. Whatever animation happens after frame 40 is not registered as the idle animation anymore. Further animations are on that same timeline.
Here the green downwards arrow is the keyframe I changed the root animation attribute to "none" (0, 40, 80, 120, 160, 200), and any red downward arrows designate a new animation (10 idle, 50 move, 90 move2, 130 attack, 170 death). The horizontal green and red arrows show the length of each of the animations.