Sir Roger (70), a former Labour finance minister and Act party founder, announced on Friday he would stand for Act as an electorate candidate at this year's general election.
The announcement, made at the Act annual conference in Auckland, was welcomed by activists.
Just where he will stand has yet to be decided.
However, Sir Roger said it would most likely be a South Auckland electorate, near where he lives, in Hanua.
The announcement ends a long and difficult estrangement between Sir Roger and Act party leader Rodney Hide.
Sir Roger turned his back on the party when Mr Hide took the reins, saying it had moved from being a party of policy substance to a reactive headline hunter.
In recent weeks, there has been talk of reconciliation, culminating with Mr Hide announcing Sir Roger had ‘‘committed his formidable skills and experience to the 2008 Act campaign''.
Sir Roger told media his decision to stand was motivated by the growing divide between New Zealand and Australia.
‘‘It's time a lot of New Zealanders stopped sitting on the sideline".
‘‘When New Zealand gets to a position where we are $100 a week in wages lower than Tasmania we ought to ask ourselves what are we doing to ourselves.''
Sir Roger dismissed suggestions his decision to stand for Parliament was not a choice many pensioners would make.
‘‘I will put in a lot of energy. I will be supporting Rodney.
‘‘I will be trying to cover some of the ground he will not be able to.''
One of Sir Roger's jobs will be putting together a full slate of candidates, and he has already started that task.
‘‘He [Mr Hide] can concentrate on marketing our policy and I can concentrate on the nuts and bolts.''
Sir Roger was quick to deny he was a fair-weather friend.
‘‘I don't think I abandoned them - I was just giving them some help on the sidelines.''
The healing of the rift between Sir Roger and Mr Hide was motivated more out of ‘‘the mess Helen Clark is making of this country'' rather than a change of Mr Hide's leadership style, he said.
Sir Roger acknowledged Act's low polling, but said it would be harder to get to 2% than it would be to get to 7%.
‘‘If we get to 2 or 3 [percent] then we become relevant and then we'll get to 7 or 8 [percent].''
