What is the name of this 70's or 80's movie?

I'm trying to remember the name of a movie I remember watching on one of the movie channels when I was a kid. It must have been a late 70's or early 80's flick.

Basic plot...

There is a group of young traveling through a desert world with crazy gangs across the land out to stop them (sort of like the Mad Max series). Oddly I recall one or more of the main characters were running around in the desert on rollerskates (rollerblades even?), and maybe even used a hockey stick as a defensive weapon. Anyway, the real plot of this movie is that water has become an item of rarity. Along their journey one of the lead characters finds her father out in the desert, and he leads them to his secret underground city where they have managed save a large deposit of ice usable for clean drinking water. His people have managed to disguise themselves in the desert wearing arabian style garments (face shawls and headdress). Something goes horribly wrong (they are invaded/attacked), and they are forced to split up again. Eventually two of the main characters are kidnapped by the real vaudevillians, and taken to some weird castle with a laboratory and a Robbie the Robot type of character. I think they eventually learn that these villains are the reason that the world hasn't produced any rain for so long. The lab is destroyed, and in the end it finally rains on the desert, and they are reunited again.

Does anyone have ANY idea of this strange movie I'm talking about? I always thought it was called Rollerball or Roller-something, but whenever I look up that name it turns out to be another dumb movie about Roller Derby, not at all the movie I am thinking of.