To use ROS, add these variables to your environment:
ROS_MASTER_URI <HTTP address of the host running roscore>:11311
ROS_ROOT %%PREFIX%%/ros/ros
ROS_PACKAGE_PATH %%PREFIX%%/ros/stacks:/my_other_ROS_directory
PYTHONPATH ${ROS_ROOT}/core/roslib/src

If you intend to build software with ROS:
CPATH %%LOCALBASE%%/include
LIBRARY_PATH %%LOCALBASE%%/lib
MAKE %%LOCALBASE%%/bin/gmake
ROS_BOOST_ROOT %%LOCALBASE%%

Note that some scripts in %%LOCALBASE%%/bin will not work, which is by design.
See http://www.ros.org/reps/rep-0100.html#ros-root-bin-executables :
> The inclusion of ros_comm and rx executables with the ros stack is
> unfortunate.  It does not significantly increase the size of the ros stack as
> binary executables will be replaced with bash scripts, but it does add
> non-functioning executables to a bare ros installation.