When I run "rox -m" in ssh it complains that it does not have an open screen, when the "rox -m" command only gets the mime type of a directory.
We need to let GTK+ parse the command line first before we can check for the -m option. To do it the other way around would greatly complicate the command line parsing. We'd also have to modify the type code to not lookup the icons under some circumstances.
Have you tried using ssh -X ?
To circumvent this (because I guess this bug will never be solved unless the command line parsing gets re-done), simply use file command (part of base installation of almost every distribution):
$ file -b --mime-type somefile
$ file -b --mime-type someotherfile