In 1988 he was sentenced to preventive detention for a further three counts of rape and one of abduction.
Preventive detention is an indefinite term of imprisonment and release can only be approved by the Parole Board.
Those attacks were committed while Carroll was on parole.
He was released in 2003, initially living north of Wellington.
It was then revealed he was frequenting a massage parlour, spending up to five figures.
He would turn up dressed in military uniform.
When his activity was made public, he moved himself into a live-in treatment centre in Christchurch.
He was recalled to prison after absconding from that centre for 17 hours.
Carroll was refused parole last year but at a hearing on August 19 the board agreed the recidivist rapist could be released.
He will leave prison on September 28.
Parole Board panel convenor Neville Trendle said Carroll's last release failed because of the "disintegration of his release plan".
"His recourse to alcohol contributed to the situation," he said.
"Since his return to prison, Mr Carroll has completed the Adult Sex Offender Treatment Programme, the Special Treatment Unit Rehabilitation Programme and the Drug Treatment Programme.
"Progress was initially slow.
"Fifteen months ago, however, when he last appeared before the board ... a significant change over the preceding period was remarked on."
Carroll told the board his improvement came as a result of him participating in the
Māori Focus Unit.
As a result, the board supported Carroll progressing into reintegration activities.
Since then, Carroll has been residing in Te Whare Oranga Ake - a unit specialising in training and repatriating prisoners to life outside.
Trendle said Carroll had been "fully participating" in the unit's activities and had been engaged in the release-to-work programme but that had to be stopped because of Covid-19 restrictions.
"He has developed a significant support structure consisting mainly of
well-established support organisations," Trendle said in the Parole Board report provided to the Herald.
Carroll's lawyer Michael Bott told the board the offender had "turned a corner prior to his last appearance" and had "come a long way since then".
"His next challenge was to transfer the structure that he had established into positive support in the community," Trendle said.
"In particular, his engagement with the psychologist had led him to better manage his emotions and to develop his insight into why he offended," Trendle explained.
"Mr Bott submitted he had demonstrated the ability to apply the skills he had acquired over a range of activities in the last period.
"He was now ready to return to the community."
Carroll told the board he conceded that previously he had been resistant to engaging with psychologists owing to historic experiences.
But he had come to the realisation that "it was he who had to change".
The board also heard he had recently been exposed to Tikanga Māori, which led to him feeling "valued and worthwhile".
"He grew in confidence in himself and was able to accept the challenges that were before him," the parole decision stated.
"He said that he felt as if he belonged."
Trendle said there had been "a striking change" in Carroll since his last appearance in May 2019.
"Progress has continued," he said.
"He has completed 59 treatment sessions with the psychologist between July 2018 and April of this year.
"He spoke positively of that engagement and what it has meant to him to change his perspective on his place in the community.
"The board is of the view that the change remarked on at his last hearing is now well established. We put that down to the combination of his experience in the Māori Focus Unit.
"We are satisfied that there is ample evidence before us of that change and also that Mr Carroll has been diligent in assembling support that will facilitate his safe return to the community."
Trendle said the board, in making its decision, had not overlooked the seriousness of Carroll's offending.
"He has an extensive offending history of serious sexual offending," Trendle said.
"We are also satisfied that the position he finds himself in today is far different from that which accompanied his last release from prison in 2003."
This time, Carroll had a developed relationship with Corrections' community service and would have the ongoing support of Māori Focus Unit facilitators.
"He will have supported accommodation and other support from organisations in the community," Trendle said.
"We have reached the view that any residual risk can be managed in the community on parole conditions.
"Accordingly, we direct his release on parole on 28 September 2020, when supported accommodation becomes available to him."
Carroll will be subject to standard parole conditions for the rest of his life.
Special conditions will be in force for five years - including a curfew from 8pm to 6am.
And he must tell his probation officer "at the earliest opportunity" details of any intimate relationship which commences, resumes, or terminates.
He will also be subject to a condition that he is not to use, possess or consume alcohol, controlled drugs, or psychoactive substances.
"Finally, we have imposed electronic monitoring in the form of partial residential restrictions and also the monitoring of his whereabouts," Trendle said.
"Those conditions may be subject to further consideration at the monitoring hearing."
Carroll has been ordered to see the board again to monitor his progress in February.