The convicted killers of Stephanie Ann Roper were sentenced to additional prison terms yesterday for rape, marking an apparent end to a three-year saga that started with the savage murder of the 22-year-old Frostburg State College student and spawned a statewide crusade for stiffer sentences and victims' rights.

The sentencing of Jack Ronald Jones and Jerry Lee Beatty doubled the minimum time they must serve before becoming eligible for parole from about 12 to 24 years.

Prince George's County Circuit Court Judge Jacob S. Levin sentenced Jones, 28, to a life term to be served after the one he is currently serving for Roper's murder. He sentenced Beatty, 20, who had pleaded guilty to raping Roper and agreed to testify against Jones before he, too, pleaded guilty, to an additional 20 years in prison, also to be served after his life term.

The men earlier had received concurrent sentences for the crimes, making them eligible for parole in as little as 12 years and leading to a public outcry that prompted Prince George's County State's Attorney Arthur A. Marshall Jr. to prosecute Jones and Beatty for their acts at the start of the crime spree.

"That was as much as we could have hoped for," said Roberta Roper, the victim's mother, who watched the sentencing with her three sons.

Roberta Roper, transformed by the murder of her oldest daughter from a part-time art teacher who led a quiet, family-centered life in the rural village of Croom into a tireless advocate of victims' rights, said she felt "a sense of relief that this chapter in our lives is closed."

Addressing Levin before being sentenced, both men said they were sorry. "I would give my own life to bring her back, if that were possible," Beatty said.

But Roberta Roper, who cried quietly during Beatty's statement, said later, "What they have done . . . to my family cannot be changed by a few words. We sometimes confuse contrition and forgiveness with justice."

It was in the early morning hours of April 3, 1982, a month before she was to graduate from Frostburg State, that Stephanie Roper was abducted by Jones and Beatty after her car broke down on a Prince George's country road. The men raped, beat and fatally shot her in the head, then set her on fire, abandoning her mutilated body in a shallow stream in St. Mary's County.

Jones was convicted of kidnaping, rape and premeditated murder after a trial in Baltimore County in which prosecutors had sought the death penalty. Beatty pleaded guilty to the same charges in an Anne Arundel court.

The perception that the initial sentences were overly lenient also spurred the formation of the Stephanie Roper Committee, a statewide group that lobbies for tougher criminal laws.

The committee counts among its accomplishments legislation increasing the period before those serving life sentences in capital cases are eligible for parole and permitting juries in such cases to read "victim impact" statements.

Currently awaiting the signature of Maryland Gov. Harry Hughes are bills requiring that victims be notified when their attackers are coming up for parole, and permitting victims to remain in the courtroom during trials rather than being excluded as potential witnesses.

Jones' mother, Lillian Jones, said she thought the sentences were too harsh.