It depends on the roofer. At least 1/4 inch. For a clean look. Let them overhang. Then once roof is completed. Snap a chaulk line and cut all at once. Some roofers do it like this others cut as they go.
We cut as we go in the winter.But Spring,summer and fall we pop a line and cut the rake immediately after the rake is installed.Some guys use the knuckles on rakes but I require a line.I feel if the starter is on a line and the shingles are being cut using a line the error of a sloppy and chewed up rake line falls on the roofer.
Well isnt this interesting..
Roofing company came today and the guy said that the guys that came last week installed wider drip edge as the eavestroughs that we had installed previously push up on the drip dge not allowing the water to drip properly?? Anyways he said that they came last thursday removed the old drip edge and installed half of the drip edge but had to stop due to ice build up. I stopped him there and said listen ime not saying your lying to me but I watched them all the time in the drive and they installed the new drip edge over the old drip edge.. he wasnt aware of that so i bet someone gets a lecture this afternoon...!