RocketLauncher Wiki is always a good source to check first for information:
https://www.rlauncher.com/wiki/index.php/Bezels
The bezel files inside each game folder need to be named "bezel something" like bezel 1, bezel 2 or bezel name, bezel other name. Then each need to have also the corresponding .ini file named the same as the bezel files with the coordinates inside.
Example:
RocketLauncher\Media\Bezels\NAME OF SYSTEM\NAME OF THE GAME\bezel 1.png
RocketLauncher\Media\Bezels\NAME OF SYSTEM\NAME OF THE GAME\bezel 1.ini
RocketLauncher\Media\Bezels\NAME OF SYSTEM\NAME OF THE GAME\bezel 2.png
RocketLauncher\Media\Bezels\NAME OF SYSTEM\NAME OF THE GAME\bezel 2.ini
RocketLauncher\Media\Bezels\NAME OF SYSTEM\NAME OF THE GAME\bezel name something.png
RocketLauncher\Media\Bezels\NAME OF SYSTEM\NAME OF THE GAME\bezel name something.ini
All this info and more in the RL wiki link above.