The result also means the Titans remain winless and firmly entrenched at the bottom of the Zurich Premiership standings. But Rotherham could feel a touch hard done by after camping on the Saints line for long spells.
England's powerful World Cup winger Ben Cohen and Spanish international Oriol Ripol scored for the Saints, while Rotherham's try came from Guy Easterby.
The scoring was opened in the fifth minute by Jon Benson, who slotted a penalty goal for Rotherham.
But that was equalled by Shane Drahm, for Saints, four minutes later.
Rotherham again went ahead in the 13th minute, when Easterby went over for a try, but that was to be their last score of the day.
In the 23rd minute Ripol scored his try, as Saints, again, levelled the scores.
Drahm, who missed the conversion, slotted a penalty on the 40-minute mark to give his team an 11-8 lead at the break.
The only points in the second half was Cohen's try in the 51st minute, with Drahm adding the conversion.
Saints shut the Titans out in the final quarter, to earn four valuable league points.
For Northampton Saints:Tries: Ripol, CohenCon: DrahmPens: Drahm 2
For Rotherham Titans:Try: EasterbyPen: Benson