Yes I think that's what they did was use rollers and a magnetic head and a gyro or dead weight to keep the rollers inside level. I seen the you tube video of them dismantling the toy sphero bb-8 remote control.
https://www.youtube.com/watch?v=5FHtcR78GA0
This is the patent I did for a magnetic sphere wheel, it uses electro magnets and no rollers. Imagine Sphere wheeled roller blades, you could stop like you on ice skidding sideways.
http://www.ic.gc.ca/opic-cipo/cpd/eng/p ... sic_search