This result now sees the Boars only three points shy of table topping Cuckfield after Matt Davies’ side chased down 231 on the penultimate ball.
It was all change at the summit as Roffey climbed from third to narrow what was a 17-point gap on then leaders East Grinstead, who slipped two places, after Horsham inflicted a first defeat on them.
Roffey’s victory came despite some fierce resistance from Middleton’s Angus Robson, who made a superb 150, after the away side won the toss and elected to field.
The decision paid dividends as Middleton struggled to impose themselves in the opening few overs of the game.
A superb bowling spell from George Fleming (3-65) saw him take three wickets without the opposition adding to the scoreboard, which was on 38-5.
Robson was proving a thorn in the side for Roffey, but a 52-run partnership between himself and new batsman Jamie Thompson (21) was cut short as the latter was dismissed by Rohit Jagota (2-28).
It was up to Robson to drag his team to a respectable score, which he did; gaining his century - making 150 - before he was removed by Jagota.
His superb knock came off 166 balls, including 17 fours and five sixes, as he propelled his side to a competitive target of 231.
Roffey opener Theo Rivers began accumulating runs before he lost his wicket for 21. Jibran Khan was soon to follow after only adding 13, then Ben Manenti was removed without troubling the scoring.
Josh Fleming (two) was bowled by that man Robson to leave Roffey were flagging at 70-4 and in need of a good partnership.
This was provided by Jagota and Usman Khan as their stand of 85 helped Roffey to put their noses out in front. Jagota made his half- century before being taken lbw for 63.
Khan’s much-needed knock of 73 was ended by none other than Robson, who proved he is just as effective with the ball as with the bat, finishing with figures of 3-26.
Chris Webb (20) was the last wicket to fall, before George Fleming and Harrison secured the winning runs, which came from the penultimate ball.
Now second-placed Roffey welcome Preston Nomads, in fifth, for a league fixture on Saturday.