Hello,
The easiest way is to create an alert rule that will let you know if new roles are assigned to users in your subscription.
From the Azure portal, go to Monitor > Alerts > New Alert Rule > Create Alert. There you can specify that you want to be alerted when a role changes for a user. The document says, "For example . . . you might want to get notified if any new roles are assigned to a user in your subscription."
You can also use Privileged Identity Management to configure alerts on role changes.
Hope this helps. Let us know if you've any other questions
Sourced from MSDN