Nice illustration from MSFT documentation that highlights the differences between Azure AD Roles, Azure Roles, and Classic subscription admin roles.
My favorite excerpt from the doc:
To better understand roles in Azure, it helps to know some of the history. When Azure was initially released, access to resources was managed with just three administrator roles: Account Administrator, Service Administrator, and Co-Administrator. Later, Azure role-based access control (Azure RBAC) was added. Azure RBAC is a newer authorization system that provides fine-grained access management to Azure resources. Azure RBAC includes many built-in roles, can be assigned at different scopes, and allows you to create your own custom roles. To manage resources in Azure AD, such as users, groups, and domains, there are several Azure AD roles.