A drugged and disqualified driver who killed a friend in a car rollover in South Australia's Riverland has been jailed for almost four years.

Jason Kyle Ramsay pleaded guilty to one count of aggravated causing death by dangerous driving and one count of aggravated causing harm in relation to the crash in May last year.

Sentencing the 21-year-old on Wednesday, District Court Judge Ian Press said Ramsay should not have been behind the wheel as he was already banned from driving.

"That you also decided to drive so soon after consuming methylamphetamine suggests a complete disregard for your obligations and responsibilities on the road," the judge said.

Immediately prior to the crash, Ramsay had looked "out of it" according to a passenger in the car who hit him two or three times to get him to come to.

"But it was too late. You were about halfway through a sweeping curve but you continued in a straight line and left the road," Judge Press said.

"You crashed into a concrete drain and the vehicle flipped onto its roof."

Adrian Hobinchet, 24, was killed in the crash while another man suffered serious injuries including a broken ankle, lung contusions and a perforated bowel.

The court heard that victim impact statements from the dead man's family spoke of their dreadful sense of loss and their struggles to find a way to move forward.

"Whilst I doubt you need to be reminded, it is clear that your actions on that day are having long-term consequences for other people," Judge Press told Ramsay.

"It is to your credit that you have written to Adrian's family. It is to be hoped that the understanding and compassion each of them have shown towards you is something you will keep at the forefront of your mind upon your eventual release."

Ramsay was jailed for three years and 11 months with a non-parole period of three years and six days.

He was also disqualified from driving for 10 years.

Judge Press said it was important to stress that the sentence could not purport to represent the worth of the dead man's life or the pain his family felt.

"No sentence will ever be able to do that," he said.