The directors' companies, Nikolai Valkov's employer Koseoglu Metal Work, and the warehouse's owner Ozdil Investments, were also convicted of corporate manslaughter and HSW Act offences and fined a total of £1.06m.
Valkov, 63, died in hospital after falling through a rooflight at the Harlow premises on 13 April 2015.
Ozdil Investments' directors, brothers Firat and Ozgur Ozdil, had contracted their friend Kadir Kose, who owned Koseoglu Metal Work, to carry out roof repairs on the warehouse.
Both the Health and Safety Executive and Harlow District Council had warned Ozdil Investments about the hazards of roof work and the need to install fall arrest measures such as netting or harnesses before the work started.
Despite this, the Ozdil brothers paid Kose and his company Koseoglu Metal Work to carry out the repairs without a risk assessment or safety measures. Bulgarian Nikolai Valkov was working on the roof when he stepped on the rooflight and fell through, hitting the concrete floor below and sustaining fatal head injuries.
After an investigation by Essex Police, in September 2016, Koseoglu Metal Work admitted charges of corporate manslaughter and Kose pleaded guilty to a charge under failing to protect Valkov contrary to S 2.1 of the HSW Act. Ozdil Investments denied corporate manslaughter and a failure to protect Valkov under s 3.1 of the HSW Act. The Ozdil brothers also contested separate charges under the HSW Act.
In a four-week hearing which concluded in February, Chelmsford Crown Court heard from prosecutor Christine Agnew QC that the skylight was not obvious and the roof was covered in dirt and lichen, according to the East London and West Essex Guardian.
The court heard Koseoglu Metal Work, which specialises in architectural metalwork, had no experience of roofing and Kose charged the Ozdils approximately £100,000 less than would have been expected to secure a competent roofing contractor.
"Faced with the evidence against him, Kose and Koseoglu Metalworks admitted their guilt but the Ozdils and their company contested the charges," said Luke Bulpitt, specialist prosecutor with the Crown Prosecution Service. "However, having heard the compelling case put forward by the prosecution, the jury returned guilty verdicts."
On Friday, Firat Ozdil was jailed for one year, Ozgur Ozdil for 10 months and Kose for eight months. All three were disqualified from being company directors for 10 years.
Ozdil Investments was fined £500,000 for the corporate manslaughter offence and £160,000 for the HSW Act offence, plus £53,115 costs. Koseoglu Metal Work was fined £300,000 for corporate manslaughter and £100,000 for the HSW Act offence, plus £21,236 costs.