The winger’s decisive strike came after a 3-3 draw in normal time, in which Victor Fernandez had netted twice and Matty Longstaff had also found the target.
The tie went to a sudden-death period of four against four, and it was Roberts who popped up with the winner to send United through to the final.
The young Magpies had booked their place in the last four with a thrilling penalty shoot-out victory over Japanese outfit Kashima Antlers in the quarter-final.
The tie initially finished 0-0, before another spell of four against four – in which defender Owen Bailey took goalkeeper Nathan Harker’s shirt in a tactical move – failed to yield a winner, despite Dan Barlaser’s best efforts, and the tie went all the way to penalties.
There, Bailey, Fernandez, Barlaser, Roberts, Luke Charman and Kelland Watts all converted from the spot, before a fine stop from Harker – back between the posts for the shoot-out – gave Matty Longstaff the chance to roll home the winner.
That set up a showdown with reigning champions Leicester, and Roberts almost gave United an early lead, but saw his shot saved inside the opening two minutes.
But just seconds later, they did go ahead when Fernandez whipped home from the edge of the box after Bailey had won a tackle to give him the opportunity.
However, the Foxes went straight back up the other end and levelled the scores. Josh Okpoda-Eppiah was the scorer, prodding home a cross at the back post to equalise.
And they moved ahead soon after, when Alexandru Pascanu was given time and space on the edge of the area before planting a low shot beyond Harker and into the bottom corner.
But Ben Dawson’s side were handed a chance to level on the stroke of half time, as Fernandez was felled in the area. He picked himself up to calmly slot home the resulting penalty, making it 2-2 at the break.
Second half substitute Longstaff made an immediate impact, cutting inside to put his team back in front once more.
But Okpoda-Eppiah’s low strike brought Leicester back into the game once again, and ensured that the contest would go to a period of four against four.
Bailey took over the goalkeeper’s jersey again, but he turned provider for the game’s pivotal moment, sliding a fine through ball through to Roberts, who netted the winner.
The Magpies will now face either Rangers or Cagliari in the final.
Photograph courtesy of HKFC Citi Soccer Sevens