Is a standard report available listing all active users and their assigned roles?

There is not a standard report, per se.  But you can get all of this information from the system by taking the following steps:

1. In the most current period, go to Users > Update User Profile.
2. Make sure the status is set for 'Active' and click on "Search User Activation".  This will pull back a list of all of the users currently active in ART.
3. Click on the Excel icon to export all of the active users to a spreadsheet (see screenshot).