Unfortunately right now there is no bulk edit tool for changing the rom path for a bunch of games at one time. We can however use Notepad++ to do this pretty painlessly. Download it here: https://notepad-plus-plus.org/ if you don't already have it, it is free and is an amazing replacement for the version of Notepad that comes with Windows.
Here is a bitbucket feature request for this to vote for: https://bitbucket.org/jasondavidcarr/launchbox/issues/1369/bulk-edit-wizard
To start off g