Approach to get relative rotation values using joints and the joint probe.
There is a method to measure rotation between two points using a fully free joint connection. This method will require a re-solve of the system but you can setup your model in all locations where you wish to measure rotation.
In the following simple example, we will be bending a simple cylindrical beam to relay the procedure.
The first step is to add coordinate systems at the location you wish to make your measurements. These coordinate systems should not be defined by geometry but rather defined by global coordinates. However, you can select the desired location by geometry and then change to global to make the process a little easier..
Now add remote points and scope them to the geometry selection you desire to measure your rotation between. Each remote point's coordinate system will be associated with the respective system that was created at their location.
Now, connect the two remote points using a general joint that is free in all DOFs. The rotation is going to be relative to the reference selection's coordinate axis.
Once solved, you can now add a joint probe to measure the rotation.