What lost head nails are to nails, countersunk screws are to screws. That is to say, they are designed to sink fully into whatever they are being screwed into, creating a flat surface rather than resting above it.
Countersunk screws achieve this via two design features. The first is that they have a flat head so once the head begins to enter into the material the flat finish is achieved. The second is the use of a tapered head into the screw itself, meaning that the head can more easily be driven into the material.
If you want a flat finish with your screws you need countersunk screws. Fortunately, at ERoofing we have you covered with a superb range of countersunk screws, made by trusted brands like SPAX®.