Many things may go wrong with low-slope (flat) roof system and there is no “bullet proof solution”.
There are many roof system components not necessary comparable with each other.
There are many different ways of proceedings to accomplish the end result, as long as you are well aware of what the end results should be. Somebody's way of “covering” one issue may cause other to fail.
Deep understanding and being aware of what may go wrong is a key to design low-slope (flat) roof assembly.
Making sure that the project is done as it was designed is the other key to success.
Low-Slope (Flat) Roofing Failures