Ansys Employee
You'll need a surface facet (post processing points don't move with the mesh) and monitor the x, y & z coordinates on that facet with time. Assuming that point is directly below the centre of rotation (I'd pick a facet on the keel) you can use Excel and trigonometry to figure out the roll angle. You could use an Expression, but if you retain the raw data you can also use it to calculate the pitch (lengthways motion) too.