"This sentence will, I hope, make other like-minded people think before they behave in a similar way to you, and also reassure the public and visitors to our country that this sort of behaviour will not be tolerated."
Isagba was found guilty of grievous bodily harm and robbery following a trial last month.
He had admitted a charge of violent disorder and two counts of burglary, all committed the same day.
Mr Rossli was cycling along a flyover in Barking, east London, when he and a friend, Sheikh Azher, were attacked on August 8.
The student did not see Isagba when he launched the assault, and after punching the victim, the teenager was seen riding off on the bike.
The incident, which was captured on camera, drew widespread publicity last year.
In the second crime against Mr Rossli, John Kafunda, 22, was caught on camera lifting the injured student up and appearing to shepherd him from trouble.
However, within seconds he and Reece Donovan, 22, began rifling through Mr Rossli's rucksack while his back was turned to them, and robbed him of a PSP games console and 10 games worth £500.
The incident was filmed and posted on YouTube, prompting widespread condemnation.
During the Isagba's trial the judge took the unusual step of lifting reporting restrictions due to the public interest in the case created by the video.
The men were unanimously convicted of robbery and violent disorder by a jury at the same court last Friday.
The judge imposed a 54-month sentence for Isagba's attack on Mr Rossli, and the same term concurrently for his robbery of him.
But he said that was in addition to a total of 30 months for the other offences he had committed.
Mr Rossli, 20, had been in Britain for just a month when he was set upon as looting swept the country last August.
The accountancy student had been cycling to help a scared female friend when his jaw was broken in two places as he was punched in the face.
Judge Pawlak told Isagba that the case epitomised the best and worst aspects of society today.
He said the best aspects were demonstrated by members of the public in the case. At least three who witnessed "horrible events", and came forward to help the police identify and catch criminals, and then the careful police work that followed.
Isagba took a leading part in violent disorder carried out by a group of 50 to 60 people, mostly hooded and many masked, in Ilford, the judge said.
Isagba had pleaded guilty to burglary at two shops which were attacked, stealing a quantity of cash, plus alcohol, cigarettes and groceries.
The judge added that Isagba appeared to target Mr Rossli due to his small build.
"You picked on him, despite the fact that others had already left him alone as he came through the crowd.
"With one punch you fractured his jaw in two places, leaving him dazed and bleeding.
"Two days later he had surgery, and two metal plates inserted which will remain with him for the rest of his life as a permanent reminder of your brutal and impulsive behaviour.
"Why did you do it? In court, you said you took the bike because you were very tired.
"You deliberately targeted him to rob him."
