Not sure exactly where the files would be. But, if you are creating masks for your roto then the keys should be saved in the project and you shouldn’t need anything that is cached. If you have the footage saved and linked that is the only external element that should be needed. That is if I am understanding you correctly.
Like I said, if you created the keyframes on a mask layer, the only thing you need is the keyframe info on that layer. If that isn’t there maybe you opened an earlier version or saved it someplace else and you are opening an earlier iteration?
Three things that might help out is to create an organized project folder (if you haven’t already), save often to that folder using the save in increments function so that you have back ups if something goes wrong, and finally, at the end of the day, collect your project and save it on a different drive – just as a backup.
Good luck and I hope this helps.
Andrew Manzella
2d/3d Geek