I have been able to get a stepper motor to rotate and have understood controlling it's revolutions.

Note all voltages are DC.

There is a Stepper Motor Driver, this is rated at 9v to 42v. It doesn't do anything if you feed it less than 9v.

The stepper motor I have is rated at 3.6v bit on doing some reading around this can be taken higher.
Using the sig gen to generate a 5v square wave initially I could adjust the frequency thus the speed. Also I was able to change the Duty Cycle quite significantly.
The maximum frequency was approx 19.5 kHz. I didn't note the current consumption but it was approx 200 mA at 11 v. No idea about the torque level but this is quite a pleasing outcome. I will see if I ramp the frequency using the sig gen and see if it 'sings' as I expect it to.

This does start to put thoughts about power of the Rover. Will need at least 10v but may want to have something higher for 'traction' but stick to 5v/3.3v for the electronics.
Also as one of the areas to explore will be to mount some Photo Voltaics to recharge some batteries I will need to consider this carefully.