Denworth Salmon, who was working with Ojewunmi on the Minerva estate, said he looked up to see someone falling. He said: "He hit the floor and the helmet came off."
Salmon said that he was still breathing but blood was pouring from his head. He added: "An ambulance was called and later that day a police officer said he had died."
Ojewunmi, who was born in Nigeria, worked for Procontract Services of Wembley, north-west London, which was carrying out a refurbishment for Tower Hamlets council.
Procontract director Trevor Warmington told the jury that his company had been carrying out external wall installations.
He said: "I heard Ojewunmi was over the parapet wall and on to the canopy areas. I don't know why he was there; there was nothing to do there. You only have to look down to see that it wasn't somewhere you should go." He said most of the scaffolding had been removed around the building but some remained to allow access on to the roof terrace and lift tower.
Health and Safety Executive inspector Nick Patience said: "Following an investigation it has been concluded there was a safe system of work in place but Mr Ojewunmi didn't follow it."
The jury returned a verdict of misadventure.