Retroarch Mame is not bad if using a new git build of the core that is not available through the updater, you can find them on the forums though. Even though it isn't bad the stand alone versions of Mame are still better overall.
If you do want to use RA Mame though there is nothing special with bios, just leave them in the folder with the roms like with stand alone Mame. And as far as using it though LB is concerned just use it like any other core. Set your emulator to Retroarch with the command parameter to use the mame core dll.