I scanned the directory containing MAME 0.185 ROMS (non-merged) but the games don’t appear in the XMB menu like Nintento, Genesis etc. I also tried split and merged. None of them appeared in the menu. The games work, though, if I manually load content. Any ideas?
You should use ‘Retroarch Playlist Buddy’ in Arcade Mode (‘search XML dat’) and point it to a valid MAME Dat file. Then it will generate a playlist for you with the proper game names, which you can then rename to Mame.lpl and put in your Retroarch/playlists dir.
Thanks for the info, daninthemix 
Retroarch Playlist Buddy? Sounds interesting. Where can I find it?
Click Download here: https://github.com/markwkidd/ahk-retroarch-playlist-helpers/blob/master/compiled-scripts/RetroArch%20Playlist%20Buddy-2017-02-10.exe
Perfect! Thank you. Not too much tweaking to get this to work. I’m grateful for that.