Hello @EnterpriseArchitect
Thank you for reaching out. "Remove-MgDirectoryRoleMemberByRef" is a Microsoft Graph PowerShell equivalent command for Azure AD PowerShell command "Remove-AzureADDirectoryRoleMember".
The new command should work the same way and remove specified member from a directoryRole mentioned in the command parameters.
I hope this helps and fixes your issue. Please "Accept the answer" if the information helped you. This will help us and others in the community as well.