Home advantage didn’t matter as the visitors both stormed through.
Wanderers’ wonderful adventure continues as the club who have won 11 promotions since 1999 refuse to hanging around.
They won 2-1 at Bath City to earn a trip to Weymouth after a fantastic first-half display.
A dangerous early free-kick wasn’t cleared and James McShane pounced on the loose ball to fire Dorking in front.
It was 2-0 when lethal Jason Prior - a promotion winner with Havant & Waterlooville two years ago - headed Marc White’s team further ahead with 41 minutes gone.
Ryan Brunt’s late penalty for the Romans couldn’t quite inspire a comeback
Dartford earlier set up a semi-final date with Havant after turning on the second half style at Slough.
The Rebels were blitzed after the break, Charlie Sheringham’s quick-fire brace put Steve King’s team firmly in control.
It was 3-0 when Luke Wanadio cut inside and fired low beyond the helpless Jack Turner.
King said: “I thought we were excellent in the second-half and we took our goals superbly.”