The Yorkshire side have yet to get off the mark and found themselves outclassed by a rampant Saints side that scored five tries to one.
Northampton lost prop Robbie Morris to the sin bin early in the game, but the Titans' forwards failed to capitalise on the advantage.
Shane Drahm and Phil Jones exchanged penalties before Saints hooker Dan Richmond bundled over for a try that Drahm converted.
Another Jones penalty followed, but Saints responded through tries from fullback Nick Beal and scrum-half John Howard, who raced home from 35 yards.
Drahm converted both efforts – adding a penalty before half-time for a 27-6 lead.
An injury forced Jones to abandon the game early in the second half before Chris Hyndman ran in the Saints' fourth try to secure the bonus point.
Titans fly-half Jason Strange then lifted the home crowd's spirits by converting his own try, but Saints lock Rob Hunter had the last word by scoring from close-range to take the Saints to third place in the table.
For Rotherham Titans:Tries: StrangeCons: StrangePens: Jones 2
For Northampton Saints:Tries: Hunter, Hyndman, Richmond, Tucker, HowardCons: Drahm 4Pens: Drahm 3