Worcester Crown Court was told that, on 9 December 2015, Stephen Webb was installing solar panels on the roof of a barn in Hereford when he fell about 7 m through a fragile roof ridge panel to the ground below, suffering fatal injuries.
An investigation by the Health and Safety Executive (HSE) found that no measures were in place to prevent falls from the roof or through the roof.
Light Power Grp admitted breaching reg 4 (1) of the Work at Height Regulation and was fined £80,000.
The firm's director, Michael John Webb, pleaded guilty to breaching reg 4 (1) of the Work at Height Regulations He was given a 12-month community order to carry out 200 hours of unpaid work and ordered to pay costs.
"There are no winners in this tragic case," said HSE inspector James Lucas. "Falls from height remain one of the most common causes of work-related fatalities in this country and the risks associated with working at height are well known.
"This tragic incident led to the avoidable death of a young man, who had only that year become a father. This death could easily have been prevented if the company and director had acted to identify and manage the risks involved, and to put a safe system of work in place."