How to script SQL server database role permissions

SELECT 'GRANT ' + database_permissions.permission_name +

    CASE database_permissions.class_desc

        WHEN 'SCHEMA' THEN ' ON ' +schema_name(major_id)

        WHEN 'OBJECT_OR_COLUMN' THEN

            CASE WHEN minor_id = 0 THEN ' ON ' +object_name(major_id) COLLATE Latin1_General_CI_AS_KS_WS

            ELSE ' ON ' +(SELECT object_name(object_id) + ' ('+ name + ')'

                  FROM sys.columns

                  WHERE object_id = database_permissions.major_id

                  AND column_id = database_permissions.minor_id) end

        ELSE ''

    END +

    ' TO ' + database_principals.name COLLATE Latin1_General_CI_AS_KS_WS

FROM sys.database_permissions

JOIN sys.database_principals

ON database_permissions.grantee_principal_id = database_principals.principal_id

LEFT JOIN sys.objects --left because it is possible that it is a schema

ON objects.object_id = database_permissions.major_id

WHERE permission_name in ('SELECT','INSERT','UPDATE','DELETE','EXECUTE') AND database_principals.NAME = ''