Mr Wright died having been engulfed in flames after being ordered by Mr Roberts to bale 4,000 aerosol cans at the Deeside Metals site near Chester.
This week at Caernarfon Crown Court Mr Roberts, Deeside Metals and Jeyes Ltd, the firm from which the aerosols originated, pleaded guilty to health and safety breaches and were fined.
Mr Wright's family condemned the case as a "travesty of justice" and condemned the CPS for gross failings in its handling of the case.
When this was put to the CPS a spokesman said the service authorised charges of gross negligence, manslaughter and health and safety breaches against Mr Roberts in June 2009.
"The CPS had reviewed this case on three earlier occasions, but the lawyers in each review misapplied the law and advised that no further action be taken.
"A final review of the evidence by our Special Crime Division, which included a vital witness statement that was obtained in May 2009, concluded that charges were appropriate," said the spokesman.
However due to the failures of the CPS the charge of manslaughter was dismissed by the trial judge as it amounted to an abuse of process.
Families Against Corporate Killing (Fack) spokeswoman Hilda Palmer said: "In this case the behaviour of the crown prosecutor seemed to discount manslaughter even before any investigation was carried out and clearly did misapply the law and the joint protocol on investigating work-related death.
"Fack asks the CPS how many other work deaths are so incompetently investigated and what happens to prosecutors who fail so badly to comply with the law and protocols.
"What redress is there for families like the Wrights when the justice system so comprehensively fails them?
"Employers have little to fear while incompetence of this nature reigns supreme and families of workers killed are treated so badly simply for insisting on the law being followed."