Method to determine angle of a rotating stage
There are standard optical rotation stages that work as you suggest. You can use them open-loop (relative motion via counting stepper motor steps once you have zero'd them) or attach an encoder to get closed-loop positioning. An incremental encoder (the more common/less expensive type) must also be zero'd to find the absolute position, but may have better resolution than a stepper. Absolute encoders tell you the actual angle, some of them can work down to nanometer resolutions on the scale. Many incremental encoders include an index output that allows you to zero the stage without additional hardware. 

But I suspect you only require a stepper motor and home switch. 

The below one is from Thor Labs and includes a 2-phase stepper motor.