Please find attached a possible solution. For this I've used a variable called XSplinePosition to return a scalar value between 0.0 and 1.0 to represent a segment's position along the spline. This is then multiplied by the angle range and added to the start angle to get the rotation value for each segment. The final expression is:
Input1+((Input2-Input1)*XSplinePosition) - Where Input 1 = the start angle and Input2 = the end angle.
I hope that helps, please let me know if you have further questions.