Non Penetration Ballasted Racking System for Solar is a common alternative used on solar installations for flat roof, it's non penetrate, so you don't need to worry your roof will have any penetrations. The difference with other roof mount is secured way, ballast mounts are secured with weight by concrete block to secure an array to the roof and prevent wind lift or other movement , but others are secured to the roof beams of the building through penetrations in the roof.