hmm good question. There are 2 stage executable files in the stage bin directory. stage and stageros.
stage is the one compiled from the original stage files. It can be used as the original stage simulator if the libraries are linked correctly. (By default the libraries are not linked for stage, the stage library has to be added to ldconfig)
However, stage does not provide the interface to ros. So if you use stage, the simulation data will not be available to ros although it will probably still work with player.
stageros on the other hand makes a portion of the stage interface available to ROS.
It published the following topics to the ros interface, so that it would work with nodes written for ROS.
/base_pose_ground_truth
/base_scan
/clock
/cmd_vel
/odom
/tf
So if you want to run simulation in ros, you gotta use the stageros instead of stage; in order for ros to interpret the simulation data.