JMRI: DecoderPro User Guide
Roster File Details
The Roster information presented in the selection box, and used for automatic selection of a Locomotive, is stored in the roster.xml file in the JMRI Preferences directory. You can find your Preferences directory location by choosing "Locations" from the main JMRI Help menu. Click the "Open Roster Location" button to open the directory in Finder/Explorer. More information is available on the "Configuration Files" Help page. You may open your Roster file and look at it to see the format. You should only use the Roster menu to manipulate the Roster file, to ensure that it stays self-consistent.
To move the entire Roster to another computer, choose "Export Roster" from the Roster menu, select a location to save the file and then move that set of files to the other computer before you choose "Import Roster" from the menu to import it there.
To do this manually at the file level, in the Preferences directory there will be a file called "roster.xml", and a directory called "roster". You need to move the "roster.xml" file, the "roster" directory, and all it's contents. Read more about the JMRI Configuration Files.