The Eels hit back as Matt Keating dived over from dummy half, before Hayne turned provider to set up Ken Sio for an 18-6 lead.
Hayne's only blemish on the night came as he slipped attempting to clean up a grubber top gift Anthony Watmough a try, though there was more than a touch of doubt about the try with video referee taking just one look to decide Hayne had not grounded the ball.
Showing the signs of a team that looked like it had forgotten the art of playing winning football, Roberts chanced his arm just after halftime with a long cut-out pass on his own 20 metre line that sailed over the sideline.
He was punished as Jorge Taufua scored his first NRL try and the Sea Eagles were down by only two points.
Signs the month-long losing streak had begun to take its toll were clearly evident as Chris Sandow unleashed on teammate Joseph Paulo after the Eels halfback was left exposed in defence as Jamie Buhrer trampled over him to give Manly the lead.
Roberts made amends for his earlier error to set up Hayne's second just after the hour mark and the Eels were again ahead 24-20, the Eels extending their lead to a converted try via a penalty in front of the sticks before Sandow's late field goal.
-AAP