Roebuck crossed twice in the first half as Northampton suffered an eighth defeat in 13 league games this season, with hopes of a successful title defence fading fast.
It took Sale eight minutes to open the scoring when, after Roebuck had gone close, Tom O'Flaherty went over.
Northampton's Tom James was sin-binned for head-on-head contact with Roebuck in the build-up and the Saints were down to 13 men when England's Tommy Freeman was shown a yellow card for a deliberate knock-on.
Sale capitalised with a second try, England back-row Tom Curry providing a pass for the onrushing Roebuck.
England veteran George Ford converted and Sale led 12-0.
Northampton hit back in the 17th minute when England rising star Henry Pollock and Alex Coles combined to send Emmanuel Iyogun over in the left corner.
Alex Mitchell failed to convert and Sale scored again when Joe Carpenter sent Roebuck racing clear down the left wing.
Northampton had their second try when Freeman burst through a gap, with scrum-half Mitchell converting.
Shortly before half-time, Ford was yellow carded for a head-on-head challenge on Burger Odendaal as Sale took a slender 17-12 lead into the break.
Shortly after the restart, Pollock scored a fine individual try when he regathered his own chip ahead before Sale prop Bevan Rodd went over from close range.
Ford converted and then added a penalty as Sale pulled away before Northampton and England centre Fraser Dingwall's converted try late on narrowed the gap and secured a losing bonus point.
But that was as good as it got for the Saints, with Sale closing out the game in a tense finale.