@drog1998 whether a rom runs with a particular core ain't depending on the folder (that would decide which (if installed) emulators are available to choose from for the roms therein; for lr-mame-cores those would be arcade and mame-libretro.), but of its content (dumped information within the archive). You need a dump matching the cores requirements (defined/queryable within its dat/xml). Take a look at RetroPies Docs and the libretro docs about romsets. In short you need to aquire or build a rom that matches the core requirements (and don't ask for it, as that would be violating the forum rules).
