source: http://stackoverflow.com/questions/6300740/how-to-script-sql-server-database-role

With the following script a script is generated which can be used to copy a SQL database role

declare @RoleName varchar(50) = 'RoleName'

declare @Script varchar(max) = 'CREATE ROLE ' + @RoleName + char(13)
select @script = @script + 'GRANT ' + prm.permission_name + ' ON ' + OBJECT_NAME(major_id) + ' TO ' + rol.name + char(13) COLLATE Latin1_General_CI_AS 
from sys.database_permissions prm
    join sys.database_principals rol on
        prm.grantee_principal_id = rol.principal_id
where rol.name = @RoleName

print @script