The script spelling for this planet was "Rosseau V",  however several other sources, including the Star Trek Encyclopedia (4th ed., vol. 2, p. 239), as well as the episode's closed captioning, spelled it as "Rousseau V."
Visual Effects Supervisor Dan Curry used lava rocks he found in the buildings supply for this scene. He was very careful sorting the right rocks out. (TNG Season 2 DVD special feature "Departmental Briefing Year Two: Memorable Missions - The Dauphin")