Newcastle led 8-6 at halftime after a terrible opening 40 minutes with both sides guilty of squandering tryscoring opportunities in front of a big crowd of 24,518.
The Knights opened the scoring with a soft try on six minutes when captain Danny Buderus went for a blindside play finding Sa'u who sucked in two defenders before popping a short ball for unmarked Uate to score out wide.
Roberts stepped up and converted the try and soon after slotted a penalty goal to settle any nerves he might have had to make the score 8-0.
Eels prop Tim Mannah made amends for a couple of terrible play-the-balls that resulted in scrums when he barged over to score from close range in the 35th minute on the back of a penalty against Timana Tahu for a high shot.
But it would be the visitors' only try in a game that struggled to reach any great heights.
-AAP