A problem that I seem to have is that, whereas the current version of MAMEoX is based upon an older MAME release, only about a half of the rom files that are available will work. By that I mean, what I do is go to the proper sources for the "right" romsets for the newest release of MAME, and download those, and while they're exactly what the latest PC version of MAME is looking for, they are incompatible with the version of MAME that was used to make MAMEoX, and when I try to run them in MAMEoX I get an error message about them being invalid sets, that certain required files cannot be found, and the emulator will quit back to the romlist.
I don't know what might offer a solution apart from updating the version of MAME at the core of MAMEoX. Since I can see no way to acquire the old romsets, which are required by MAMEoX, I can't figure how to get a majority of the games that I want to play to work with MAMEoX.