Product Tag - roller-skating

In a future in which most water has disappeared from the Earth, we find a group of children, mostly teenagers, who are living at an orphanage, run by the despotic rulers of the new Earth. The group in question plays a hockey based game on roller skates and is quite good. It has given them a unity that transcends the attempts to bring them to heel by the government. Finding an orb of special power, they find it has unusual effects on them. They escape from the orphanage (on skates) and try to cross the wasteland looking for a place they can live free as the storm-troopers search for them and the orb.