This sample code demonstrates sending Sphero roll commands. 4 buttons on the UI will allow you to send Sphero roll commands at 0, 90, 180 and 270 degrees. The stop button in the middle will stop Sphero.
The roll command takes a heading from 0° to 360°, and a relative speed from 0.0 to 1.0. So, to command the ball to go 90° at half speed would be:
[RKRollCommand sendCommandWithHeading:90.0 velocity:0.5];
The ball is stopped with
Also, demonstrated in the code is the use of RUICalibrateGestureHandler which is attached to a view in it's initWithView: method. Calibration is used by the user to aim Sphero in a direction that they consider forward and sets the 0° heading in that direction. This gesture uses two fingers to rotate the ball similar to using two using the two finger rotation gesture used to rotate a photo.