On an opening night of not many goals, Tom Blackwell got the only one - and that came late into extra time as Braintree bettered Bath City.
After falling at this stage last season, the Iron held firm to seal their semi-final spot after finally breaking the Romans’ resistance.
It heartbreak for a third time in six years for Jerry Gill, who is still searching for that elusive promotion.
Braintree face Chelmsford City on Saturday for a place in the final next weekend with Maidstone facing Aveley on Wednesday night.
National League North Boston United head to Scunthorpe on Saturday after holding their nerve at Alfreton Town.
They continue to be very hard to score against as showed their defensive qualities to keep the Reds at bay, the game ending 0-0.
It went down to penalty kicks and the Pilgrims put all theirs away and celebrated in front of their vocal travelling fans who will travel with them in force to Glanford Park this weekend.