Do they take it out, turn it on, and let it roam around from time to time?
According to this answer, there were some initial tests and some problems about two years ago. Has there been any change of status since then?
ROS was delivered to ISS aboard a SpaceX rocket as part of a recent resupply mission that also included a set of robotic legs that will be attached to R2 soon.
NASA was able to upgrade the R2 torso earlier this month after on-orbit surgery to remove old processors and electronics and install new ones. On August 12, R2 powered up using ROS for the first time.
As we mentioned in a prior post, the R2 team at JSC has been using ROS for R2 development on Earth for the last couple of years. They combine ROS with OROCOS RTT to produce a flexible development environment with real-time capabilities.
below: From here.