I know this post is a couple weeks old and you may have already solved it, but as no confirmed resolution is posted I wanted to add to it in the event someone searches for help later.
I am doing the opposite, using VirtualBox inside Ubuntu to run a Windows VM, specifically to run ION Studio for flashing firmware and setting PID values. The two things I had to do to get VirtualBox to recognize the Roboclaw USB (actually no USB devices were shown until I did this) was to install the VM Expansion Pack and then do what acidtech linked to, add the user to the vboxusers group. That of course is if your host is Ubuntu, so with Windows as the host it seems there may be some USB filter driver that needs to be installed that allows VirtualBox to control the various USB devices and pass them through.
The only other thing you will need to do in Ubuntu (after you get access to the USB device of course) is to adjust the permissions for the dialout group to gain access to the serial port. I had to do this with python, I'm assuming C/C++ would be the same.
Something like:https://unix.stackexchange.com/question ... thout-root