Azure Global Admin without Office 365

Solution 1:

Office 365 uses Azure AD as it's identity and authentication provider. Azure AD admin roles grant permissions in both your Azure AD instance and your Office 365 tenant. When you assign admin roles in the Microsoft/Office 365 admin center you're really just assigning roles in Azure AD that are then used by the Office 365 platform (Global Admin, Billing Admin, etc.). It isn't possible to decouple Global Admin in Office 365 from Global Admin in Azure AD. It's a single role that confers permissions in both environments. Office 365 doesn't use all of the roles available in Azure AD (AFAIK), but I think it would be very difficult to assign yourself admin roles in Azure AD that didn't also give you the corresponding admin permissions in Office 365.