The Aries sees the stick, right? Do you really need a sophisticated database driven application to play a few files on a stick?
When I have files on a stick to play on my Oppo I just play them, no need for Roon.
Roon catalogs the stuff on the core or server so, as the other poster pointed out, it first has to be mounted on the core. To do that, the Aries would somehow have to become a file server seen by your core. There may, or may not, be a way to do that but even if it were, is it really worth the trouble? Roon would have to update your library and, as soon as you unplugged the stick, update it again.