Adding lot of new role assignment on different folders

On our local SSRS we are currently adding a big quantity of different users on different folders. The usual steps are like the ones detailed here SQL Server Reporting Services 2012 Permissions.

Is there a way this can be done through tsql on the report server itself? Is annoying going to each folder, clicking on new role assignment, adding the user, role and saving.

Digging in I see there are several tables involved, check the code. But still is not clear to me how can I add the groups, roles, etc, automatically generating the needed ID's.

USE ReportServer

SELECT pu.*,
       u.UserName,
       r.RoleName
FROM   dbo.PolicyUserRole pu
       JOIN dbo.Users u
            ON  pu.UserID = u.UserID
       JOIN dbo.Roles r
            ON  r.RoleID = pu.RoleID
       JOIN dbo.Policies po
            ON  po.PolicyID = pu.PolicyID