SQL DBA - How to Change\modify\drop the user role for a User

EXEC SP_ADDROLEMEMBER N'db_datareader', N'user_Name';

EXEC SP_ADDROLEMEMBER N'db_datawriter', N'user_Name'

EXEC SP_ADDROLEMEMBER N'db_backupoperator', N'user_Name'

EXEC SP_DROPROLEMEMBER N'db_backupoperator', N'user_Name'