Removing a SQL Server Database Role
The changing security requirements of a database can render a Microsoft® SQL Server™ database role obsolete. Remove roles when you have removed all users and are certain that the role and its permissions will not be required in the future. Empty roles can be saved if the permissions may be required for a new user. However, from an administrative perspective, it is much easier to work with a security system that is not cluttered with unnecessary security roles. SQL Server operates faster with a simpler security system, although it is will not be a problem unless there are an extremely large number of roles.
Note It is not possible to remove fixed server roles or fixed database roles.
To remove a SQL Server role