Nikolai Valkov, 63, died in hospital after falling through the roof of a warehouse in Harlow on 13 April 2015.
At Chelmsford Crown Court, Koseoglu Metalworks Ltd admitted an offence of corporate manslaughter and its sole director, Kadir Kose, admitted a safety offence.
Ozdil Investments Ltd denied corporate manslaughter and a safety offence but was convicted following a trial.
Two of its directors, Firat Ozdil and Ozgur Ozdil, were convicted of a safety offence.
Firat Ozdil was jailed for one year, Ozgur Ozdil for 10 months and Kose for eight months.
Ozdil Investments was also fined a total of £660,000 and Koseoglu Metal Works Ltd £400,000.
The court heard how Ozdil Investments Ltd was the owner of the warehouse where the roof needed repairs.
Both the Health and Safety Executive and Harlow District Council issued warnings to the company about the dangers involved in the repair work and specifically the need for safety measures such as netting to be put in place.
Despite this, Firat Ozdil and Ozgur Ozdil paid their friend Kose and his company Koseoglu Metalworks Ltd to carry out the work without netting or other safety measures.
The court heard Koseoglu Metalworks Ltd had no experience of roofing work and the fee paid by the Ozdils was approximately £100,000 less than a recognised roofing contractor would have charged.
Kose did not carry out a risk assessment at the site and sent staff employed by his company onto the roof without training.
While working on the roof Valkov stepped onto a discoloured skylight and fell to his death.
Luke Bulpitt, from the CPS, said: “By ignoring the safety measures they knew were required, the Odzils and their company risked the lives of everyone working on the roof in an attempt to save money.
“Kadir Kose and Koseoglu Metalworks undertook the work to the roof without taking any appropriate safety steps, gambling with the lives of their employees.
“Faced with the evidence against him, Kose and Koseoglu Metalworks admitted their guilt but the Ozdils and their company contested the charges. However, having heard the compelling case put forward by the prosecution, the jury returned guilty verdicts.
“Our thoughts remain with the family of Mr Valkov.”
The prosecution followed an investigation by Essex Police.
