Alex Webster’s 86th minute decider clinched the three points which lifted Ruthin up to second spot.
Les Brophy’s 39th minute strike gave the hosts a half-time lead, but Rhys Hughes levelled on 53.
Webster nudged Town back in front on 76 minutes, but Port were soon back on terms courtesy of Cian Pritchard.
A draw looked likely until Alun Vaughan Evans set up Webster for the winner.
Luke Baum hit the 30-goal mark in league matches as his hat-trick helped secure Talysarn the thumping win which put them third in Division One.
Baum, who has 37 goals in all competitions, netted on 30, 41 and 90+3 minutes.
Jac Jones (pen), Rhodri Jones (2), Jack Usher, Peter Bridges and Gerwyn Williams provided the rest of the away goals, Thomas Davies with a consolation for Rovers via the penalty spot.
What a game at Parc Mwd.
CPD Y Fali led 3-0, were reduced to 10 men, and then conceded three as Cefni fought back for a point.
Cai Miller put the hosts in front on three minutes and Dan Manning doubled the lead after 16.
When Marc Wilson bagged Fali’s third three minutes into the second half, it looked all over.
However, when Morgan Rowlands was red-carded for the home side, it all went downhill for them.
Nathan Lewis put away a 62nd minute penalty before completing his double on 71.
Hugh Alan Jones made it three-apiece on 80 minutes and the race was now on for the winner, with Cefni favourites to bag it with the extra man, but it never came.
It's a big Flintshire welcome to Poppy Smith. Picture: FLINT TOWN UNITED FC Flint Town…
Megan Skelly-Robinson Llangefni Town have strengthened their goalkeeping options by signing a second top-class stopper.…
Ellie shoots for goal. ALL PHOTOS: DAI SINCLAIR - DIOLCH DAI She's been there since…
Often the definition of a successful pre-season for a football club is as much about…
Samantha WiIliams, of IWT, with headteacher Arwel Owen and Ysgol Bro Dyfrdwy pupils ANOTHER GREAT…