Leaking Shed Roof

[tommyL]

I have a low pitch shed roof over an old addition that it leaking. after testing with hose determined that water is coming down main roof onto shed and under the outside long edges. had several contractors look at it, but will do myself. what is the best way to seal those long outside edges. I was going to used asphalt sheet roofing glued to deck, but how do I treat the edges to ptrevent water coming back in: glued and sealed with 40 yr silicone along edges? drip edge under the roofing? drip edge over the roofing and sealed?
Any advice is appreciated, thanks.
tom