Chris Birchall put the visitors ahead early on after rounding Joel Castro Pereira, but Ian Henderson equalised with a penalty five minutes before the break.
Dale dominated the second half and Nathaniel Mendez-Laing scored with 12 minutes remaining to secure the three points.
Keith Hill made four changes to the side that started away at Gillingham on Tuesday night. Scott Tanser and Joe Bunney returned to the starting line-up, with James Hooper making his first professional start after coming on as a substitute for his debut in midweek. John O’Sullivan, signed on loan from Blackburn Rovers on Thursday, was put straight into the first eleven.
Dale were almost ahead inside three minutes when Hooper broke at pace after a neat interchange with Calvin Andrew. He found Ian Henderson on the left side, who tried to curl an effort over Jak Alnwick in the Port Vale goal, but the goalkeeper was able to stretch enough to tip the ball over the crossbar.
The rain had been constant before kick-off and there was no let up from the heavens in the opening stages. The pitch coped superbly but the ball was holding up ever so slightly, which played a part in the opening goal. A ricochet in the Dale defence held up on its way back to Joel Castro Pereira, allowing Birchall to steal in, round the Dale stopper and turn the ball home.
It was a blow to Dale after a decent start, but Hill’s men responded well and were the better team for the rest of the half. Debutant O’Sullivan was treading a fine line though having already been booked for an accumulation of fouls. Donal McDermott came on to replace him to save the loanee from a second yellow card.
Dale continued to press through a number of corners, whilst Andrew was causing the Vale defence problems from the right channel. The Dale number nine had a great opportunity to level things for his side when he broke through one on one with Alnwick, but he fired straight at the goalkeeper who blocked well.
Sam Foley tried an ambitious chip over Castro Pereira as the visitors tried to strike on the break, but five minutes before half time Dale levelled matters from the penalty spot.
Hooper was played through in the area and touched the ball away from a sliding Carl Dickinson who brought him down. The assistant referee gave the decision which the visitors debated fiercely. However, Henderson kept his cool after the slight delay and sent Alnwick the wrong way.
Dale started the second period the way they had ended the first, pressing the Port Vale back line forcing them long. McDermott was lively sending a dangerous ball across which was well cleared, before a dipping effort from distance was just over. Bunney was replaced by Mendez-Laing for the final half an hour.
Corners were again proving dangerous for Hill’s side with Oliver Lancashire having a header cleared after he rose well.
It was all Dale and only the width of the post prevented them taking the lead. A great cross from the right by Henderson was turned onto the upright by Vale defender Richard Duffy before bouncing clear.
However, for all Dale’s pressure they could not find a way through, and the visitors really should have retaken the lead through substitute Uche Ikpeazu. He seemed to have pushed Lancashire the ground in a chase for the ball, but the referee let play continue. He came inside and went past Castro Pereira, but with only a defender on the line his effort was blocked out for a corner.
It was a let off for Dale but one they capitalised on almost immediately. A cross from the left was picked up by Hooper at the far post and fired on goal. The effort was blocked but only as far as Mendez-Laing, who fired the ball into the bottom corner for a goal Dale deserved.
The noise levels went up a notch from the home fans who felt a sense of relief as well as celebration after finally finding a way through.
Dale continued to press in an attempt to put the game to bed, but had to be solid in the five minutes of injury time which were added. Dickinson was sent off in the final minute for an altercation with Henderson as Vale lined up for a free-kick which was well held by Castro Pereira in the final action of the game.
It was an impressive performance for Dale and a deserved three points. The league takes a back seat for a fortnight now as we welcome Bury in the FA Cup next Sunday.
Dale: Castro Pereira, Bennett, Lancashire, McNulty, Tanser, Camps, Henderson, O’Sullivan, Hooper, Bunney, Andrew.
Subs: Lillis, Rafferty, Eastham, Vincenti, McDermott, Mendez-Laing, Rose.
Port Vale: Alnwick, Dickinson, McGivern, Duffy, O’Connor, Birchall, Dodds, Foley, Yates, Leitch Smith, Grant.
Subs: Neal, Purkiss, Streete, Ikpeazu, Daniel, Hooper, Kelly.