Patrick McCarthy (trading as All Care Home Improvements) was given a 14-month custodial sentence after the death of Andrei-Ionel Hutanu in 2019.
No scaffolding or other measures had been put in place to prevent falls from the roof.
Harrow Crown Court heard how 33-year-old Hutanu and another man were working at the rear of commercial premises in Neasden on 19 August 2019.
While his co-worker had been instructed to remove building materials from a flat roof, Hutanu had been instructed to carry out repair work on a tiled pitched roof. He was working on it from a roofing ladder when he fell approximately five metres onto a concrete alleyway below.
He fractured his neck and sustained other serious head injuries in the fall and despite being taken by air ambulance to St Marys Hospital in Paddington, he died a week later.
An HSE investigation found McCarthy had failed to take any steps to prevent falls from height by failing to install scaffolding around the perimeter of the building or flat roof where both men were working.
McCarthy (trading as All Care Home Improvements) of Ealing, pleaded guilty to safety breaches and received a 14 -month custodial sentence.
After the hearing, HSE Inspector Philip Jordan said: “This tragic incident could have been easily avoided. Assessing and planning work at height is essential to ensuring that suitable and sufficient measures are in place to prevent falls from height.
“The custodial sentence imposed on Mr McCarthy should underline to everyone in the construction industry that the courts, and HSE, take a failure to follow the regulations extremely seriously. HSE will not hesitate to take appropriate enforcement action against individuals or companies that fall below the required standards.”