With this function you can retrieve the index of the room after the room input into the function. For example you can use the read only variable room to get the index of the current room and then use this function to find the room that follows it in the resource tree. If there is no room after the one you input then -1 is returned.
if room_next(room) != -1
The above code will check to see if the next room exists and if so, it will go to it.