Colin Howles, 53, was photographed by a Health & Safety Executive (HSE) inspector as he and an employee replaced roof tiles on a mid-terrace house on Wyndale Road in Bardsley.
The HSE inspector issued a prohibition notice, ordering the men to come down from the roof immediately, when he visited the site as part of routine inspections in the area on 3 November 2010.
Trafford Magistrates' Court heard that no scaffolding had been put up at the back of the property to stop either of the men falling nearly six metres to the ground below.
Two scaffolding towers had been erected at the front of the house but there was no scaffolding at the rear when the men started work on that section of roof.
Colin Howles of Bardsley Vale Avenue, Oldham, pleaded guilty to a breach of the Work at Height Regulations 2005. He was fined £350 and ordered to pay £600 in prosecution costs.
Speaking after the hearing, HSE inspector Tom Merry said: "Mr Howles has more than 30 years' experience in the building trade so should have known how to carry out the work safely. In fact, he erected scaffolding at the front of the house but not at the back.
"Not only did he risk his own life, he also risked the life of another worker by allowing extensive roof work to take place without scaffolding on both sides of the building.
"It is through sheer luck that neither he nor the other worker became one of the thousands of people who are killed or seriously injured in a workplace falls every year."