All the Rocketdock user settings are stored in the windows registry.
\HKey_Current_User\Software\RocketDock
You can see them when running regedit.exe from the run command and opening the folders to get to the above path.
Go to that folder, right click and "export" the folder settings, and you've got your custom setup in a ".reg" file of your naming.
Copy that file over to the computer you'd like the settings to be also on. Install RocketDock on the new computer.
Then, use a program like SaferNetwork's RegAlyzer on that computer and right click / import on the "Software" folder that has the RocketDock folder in it to put the settings in the same place in the registry (you might have to delete the rocketdock folder first).
https://www.safer-networking.org/products/regalyzer/
You'll have to move the hard drive folder where you have the custom icons or other files you've used onto the 2nd computer as well and have all the same programs installed, of course, with the same path for these to show up correctly at first crack. You may have to adjust some program paths...
Be sure the link in the registry setting: CustomIconFolder is set to that migrated Icon path (with a ? mark in front of the path.
Note: This was for Windows 8.1. If importing to Windows 10, use the Programs 64 folder, as it has two "Program" folders there. It's the one with RocketDock already in it
Also, you may need to close and then reopen RegAlizer to see the import worked and close and reopen RocketDock to see the new settings take effect.