I suspect then that this is the method you used originally to populate the drive and then you simply connected it to the ROCK which would then become the source of your troubles.
Note: Having a way to set the timezone on the ROCK wouldn’t help because different operating systems store different timestamps (local time versus UTC) in the filesystem. Swapping drives between machines running different OS’s might always lead to discrepancies regarding timestamps. Don’t do this if you need reliable timestamps!
Maybe you can tell ROBOCOPY to correct just the timestamps of the files while connected to the ROCK?
See also the following older thread: