It is most likely in the Asian family Zephroniidae. It will be very difficult to identify it even to the genus level, let alone species. You may even own a new species. Where did you buy these from? Location will help greatly with identification.
There are some similar pictures under the Google searches for "thai pill millipede" and "zephroniidae", but none have a clear identification. Sorry I can't help more but they are a very understudied group; I doubt that most people on here will be able to identify it past the family level.
Hmm... that genus sounds fairly likely, but with these things its anyone's guess. Doesn't make them any less pretty though.
Do you have temperature information and any dietary requirements? Most of the commonly seen species in the hobby are from mountainous or cloud forest regions and require cool temperatures. Perhaps one from warm areas with a less picky diet will finally be the species to breed and have several generations in captivity.
Keep in mind that you are one of the few people in America who owns pill millipedes of any kind. I hope your work succeeds both for you and the hobby's sake!
Very nice! Id love to offer some up in the near future for people to try id prefer more experienced individuals so that they can represent this speciesI mainly focus on centipedes, but I own Narceus americanus, N. c.f. annularis, T. corralinus and A. monilicornis as far as millipedes go.