The Millers have had a wretched season and were relegated on April 1.
But their 1-0 victory over Ipswich last Saturday saw them hit the 21-point mark, providing a modicum of relief.
There had been concern they would finish with less than the 20 points Doncaster did in the 1997/98 season.
That is a record low since the Football League moved to 46-game campaigns.
Millers manager Paul Warne said: “To get to 21 points is a relief. I’m happy about the win, as I am the clean sheet.
“I am in charge of this team, I am the one who took us down, so I want to finish the season on a high.”
Last Saturday’s win was just their fifth of the season, all of them at home.
Some joy on the road is a target when they make the trip to Deepdale, a game which will see North End trying to get back on the horse after four straight defeats.
PNE boss Simon Grayson will not be taking the visitors lightly as he looks to finish the home campaign on a high.
Grayson said: “Rotherham, like any team, will be wanting to end the season as positively as they can and we have to be aware of that.
“Paul Warne has players there who will be playing for their futures.
“He will want a good end to the season, ready to start a new campaign in which they will be looking to get back to the Championship.
“Within their group, they will be hugely disappointed at how the season has gone.
“But they have one or two individuals who are good Championship players and capable of hurting you.”
Rotherham will end the campaign having had three managers at the helm.
Alan Stubbs started the season in charge, having been recruited from Hibernian to succeed Neil Warnock.
Stubbs oversaw just one win before being sacked in October, the Millers turning to Kenny Jackett.
His reign lasted six weeks, Jackett in charge when North End won 3-1 at the New York Stadium on November 5.
When Jackett quit, Warne was promoted from his job as fitness coach to caretaker manager.
Although unable to guide Rotherham out of trouble, he did enough to land the job on a full-time basis in January.
It will be a re-building job this summer for Warne.
Top scorer Danny Ward could leave despite the club exercising a 12-month option on his contract.
He could miss the visit to PNE, having limped out of the Ipswich win at half-time.
Rotherham’s winner last week came from midfielder Tom Adeyemi who is on loan from Cardiff City.
Adeyemi is a player Warne would like to hold on to.
Said Warne: “Goalscoring midfielders are gold dust.
“I’ve had a recruitment chat with the chairman.
“I’ll do everything I can to keep him but all clubs struggle to keep their best players and we are no different.”