This article has some good snobbish info about how cornice returns are supposed to look.
Roof cornice return.
Done properly this is hip cut back to the wall and the eavestrough runs all the way around back to the wall.
But there are ways to ensure they are sound.
If the overhang is 24 then it normally get s returned double that at the gable.
A cornice return is an architectural detail that occurs where the horizontal cornice of a roof connects to the rake of a gable.
This house had rotted roof rake returns.
This can be challenging because the returns are located outside the corner boards which means they require additional structural support.
Most greek revival buildings have substantial cornices that extended into gable ends as returns below picture.
Heres some terminology for you click to enlarge.
It is a short horizontal extension of the cornice that occurs on each side of the gable end of the building see picture of the härnösands rådhus with two of these.
Sometimes this helps with drainage and other times the cornice return is more of a decorative piece.
They are more properly called cornice returns i think but i d rather call them eave returns.
Also called an eave return a cornice return is a graceful way to transition the eave and the main fascia board around the gable end of a house.
A cornice return is a triangular piece of material that is placed below the rake fascia on the corner of a roof.