Snow breaks/diverters pretty much only work with metal roofs. The "breaks" are not used up here, even on metal, because nobody wants 18" if ice sitting on their roof. Diverters are used above stovepipes so the sliding snow won't tear the chimney down when it slides, but that's about it.
I think I was unclear. My shingle roof is still on under my metal roof, ergo, I do not want any additional weight on the roof.