Dale were trailing 2-0 at half-time after David Mooney opened the scoring from the penalty spot on 38 minutes, while Ryan Leonard doubled the hosts’ lead just minutes later.
But after relentless pressure from Dale mid-way through the second half, Joe Bunney pulled a goal back for Dale on 63 minutes, while Michael Rose hit the back of the net with a sublime free-kick on 78 minutes.
Manager Keith made two changes to the side that drew with local rivals Oldham Athletic last weekend with Tom Kennedy replacing the suspended Andy Cannon in defence, while Joe Bunney came in for Lewis Alessandra in attack.
Jamie Allen tested goalkeeper Dan Bentley with a low strike from outside the area on three minutes, while Shrimpers striker Joe Piggot shot wide of the post five minutes later.
Matty Lund fired narrowly over from 25 yards on 13 minutes, before Scott Tanser made an important challenge to dispossess John White inside the six-yard box.
United’s Gary Deegan launched a powerful effort that looked destined for goal – only to be denied by a fabulous last-ditch header by Peter Vincenti, who forced the ball out for a corner before the hour-mark.
Soon after, Shrimpers frontman Mooney raced through on goal and tried to place the ball beyond Josh Lillis, but the Dale shot-stopper pulled off a marvellous save to deny him – as well as thwarting Mooney’s header from a set-piece moments later.
Lillis conceded a penalty on 37 minutes when he brought down Leonard inside the area. Mooney stepped up to take the spot-kick and made no mistake by firing the ball into the roof of the net.
Before Dale could test Southend with a chance to equalise, they found themselves trailing by two goals when Leonard fired into the bottom corner on 41 minutes.
Hill made three attack-minded changes at the beginning of the second half with Calvin Andrew, Michael Rose, Nathaniel Mendez-Laing being introduced in place of Vincenti, Tom Kennedy and Jamie Allen.
Dale missed a golden opportunity on 54 minutes when Camps played in a marvellous ball to Henderson in the centre of the box, who was unable to get a touch onto the ball in the danger area, while Andrew headed narrowly over moments after.
Rochdale continued to enjoy chances with Olly Lancashire hitting the side-netting from a corner on 57 minutes, while Henderson tested Bentley with a looping header on the hour-mark, and the stopper could only parry the striker’s effort out for a corner.
Dale’s relentless pressure paid dividends when Joe Bunney found the net from a Michael Rose corner on 63 minutes.
The goalscorer, given a new lease of life after the break with the support of substitute Andrew, then went agonizingly close for Dale just two minutes later, seeing his strike from outside the area go narrowly wide of the post.
Rose grabbed a much-deserved equaliser with a stunning free-kick from 20 yards which hit the back of the Southend net like a thunderbolt with 12 minutes remaining.
Andrew burst through one-on-one with goalkeeper Bentley but his close-range effort was denied on 83 minutes, while Mendez-Laing saw his low-drive cleared by Cian Bolger.
Lillis pulled off yet another strong stop to deny Mooney on 88 minutes, as the hosts through everything at Dale in order to restore their lead.
ROCHDALE: Lillis, McNulty, Lancashire, Kennedy (Rose ’45) Tanser, Lund, Allen (Andrew ’45), Vincenti (Mendez-Laing ’45), Camps, Henderson, Bunney NOT USED: Pereira, Eastham, Alessandra, McDermott,
SOUTHEND UNITED: Bentley, White (Rea ’71), Coker, Prosser, Timlin, Mooney, Bolger, McLaughlin (Worrall ’85), Leonard, Deegan (Atkinson ’81), Pigott NOT USED: Smith, Wordsworth, Payne, Williams
REPORT BY SIMON ROWBOTHAM