We had a similar problem with our pocket doors.
Using a bright flashlight I was able to see that the rear carriage slipped off the track, likely due to someone pushing the door closed (from the bottom) with too much force. In my case I was able to pull the door out enough to grab the top part of the door. By pulling the top part of the door away from the pocket and pushing the lower part of the door towards it, I was able to raise the carriage up enough to get it to seat back on the track. I had to twist a little (push the bottom of the door away from me too) to get the top of the door to move in the direction of the track.
In my case, I was able to look at the track as well as look at how the other door worked to get an idea of where the wheels were and get an idea of how it slipped off the track. If your doors are really hard to push, both wheels may have come off. In this case, I'd suggest working on getting the outside wheels back on the track first by lifting the door and moving the top to the left and right to get it back on track.
The image above has clearer labeling of the door parts, but the image below gives a better view of how my doors are designed (they only have a single wheel and a track large enough that the wheel can jump out).