How i can check records of role changes in ARCS?

Summary:

I would like to check or download reports of role changes to any users in ARCS.

Content (required):

Hi All, i have a question about ARCS.

In ARCS, each users have a role of four kinds of roles - Administrator, Power user, User and Viewer.

Depending on the situations, it may happen that someone's role would be chaged to another role from any of four kinds of roles.

I would like to check whether it had happened role changes to any users.

Then, my question is as follows.

Does anyone has any insights on how i can check records of role changes?