The script lists all Azure AD admin roles assigned in your tenant. Only roles with active assignments are returned, along with details about the corresponding user or service principal object. The script requires the Azure AD PowerShell module. You can download the latest version here: https://www.powershellgallery.com/packages/AzureAD/
If existing session to Azure AD is detected, the script will try to reuse it. Otherwise, you will be prompted for credentials.
Questions and feedback are welcome.
Dont forget that admin roles are only one of the ways permissions can be granted in Azure AD/Office 365. If you want a comprehensive inventory, make sure to cover any workload-specific controls, as well as application permissions. With regards to this, the script goes hand to hand with the Azure AD Integrated Applications Inventory one: https://gallery.technet.microsoft.com/Azure-AD-Integrated-44658ec2?redir=0