SQL Server provides built-in database and server roles. Members of a specific role inherit the privileges of that specific role. Such implicit privileges can not be seen in security related system tables and views. We may find members of a role both by SSMS or T-SQL.
Get members of a role through SSMS
Get members of a role through T-SQL
More conveniently we may get list of role members both for database role or server role. Following script would list members of sysadmin server role and db_DDLAdmin database role.
-- Get members of sysadmin server role
EXEC sp_helpsrvrolemember 'sysadmin'
-- Get members of DDLAdmin database role
Role name may be substituted as required in both cases. Result would be 3 column list of role members.