If an Element is family instance then:
(FamilyInstance.Location as LocationPoint).Rotation;
I can easily get a rotation easily for family instance.
If I try for wall
Curve curve = ((Wall).Location as LocationCurve).Curve;
Or anything like that.
For example :
In preceding image, trying to rotate wall to 90 Degree.
In below Image, after rotating 90 Degree
Need to get the rotated angle of the wall.