Rudy Gestede rescued a point for Rovers as they showed terrific battling qualities in a pulsating 3-3 draw at Vicarage Road.
In a match in which Gary Bowyer's side were the better for long periods, they were indebted to the giant striker who scored in time added on at the end of the game.
Rovers recovered from the early shock of conceding a fourth minute Marco Cassetti goal, to roar back and level courtesy of David Dunn's volley - his 50th league goal for the club.
The visitors withstood early second half pressure, to then take the lead for the first time, Dunn the provider, Craig Conway the eager recipient.
However the Hornets were back on level terms almost instantly as Troy Deeney scored from the spot after Todd Kane was harshly adjudged to have handled.
The home side thought they had claimed an unlikely three points when substitute Cristian Battocchio scored with two minutes left of the ninety.
But in added time Rovers got the least their play deserved with Rudy Gestede's towering header from Matt Kilgallon's cross going in off the post.
Rovers can be heartened by the display, a point the least they deserved on a night when they had the lion share of possession and chances.
Gary Bowyer made two chances from the side that drew 1-1 with leaders Leicester City on Saturday.
One of those changes was enforced as Todd Kane replaced the injured Adam Henley, whilst David Dunn was preferred to Liam Feeney who dropped to the bench.
Grant Hanley was back in the squad, the defender named amongst the substitutes.
For the Hornets, they made four changes from the side that lost to Wigan at the weekend. Joel Ekstrand, Sean Murray, Tommie Hoban and Alexander Merkel in for Essaid Belkalem, Cristian Battocchio, Davide Faraoni, and Lewis McGugan.
Former Rover Lucas Neill, who joined the Hornets last month, was named on the bench.
No sooner had Rovers kicked off at Vicarage Road than the first chance of the match was created.
Todd Kane, back in the starting line-up for Rovers, advanced down the right flank before unleashing a cross-shot that almost caught out Watford goalkeeper Manuel Almunia, the Spaniard having to scramble to get the ball away.
But whilst Rovers went close with their first chance, it was the home side who converted theirs after just four minutes.
After a corner had been cleared for a throw, the ball thrust back into the area to where Alexander Merkel hooked on for defender Marco Cassetti who fired home from close-range.
Unbowed, Rovers went straight up the other end and created a host of opportunities in quick succession to draw level.
David Dunn fired over the bar after good work from Jordan Rhodes and Rudy Gestede, then a one-two between Gestede and Dunn saw Almunia deny the Benin international with his legs.
Then after the initial corner was cleared, Tommy Spurr launched the ball back into the box but Gestede could only nod inches over the bar.
After that flurry of Rovers chances inside the first ten minutes, play settled down with the Hornets starting to carry a threat once more through Troy Deeney and Ikechi Anya, but Rovers were composed defensively and eventually got their deserved equaliser on 27 minutes.
After David Dunn had drawn a clumsy foul from Daniel Tozser, Craig Conway took the resulting kick, Almunia failed to connect cleanly with his punch and Dunn met the ball perfectly on the volley to fire it home from the edge of the box.
It was the Rovers' stalwart's 50th league goal in blue and white.
Five minutes later and Dunn was hunting his, and Rovers, second of the game. After taking down a Gestede flick, the midfielder took the ball around Cassetti, but the defender got back in the nick of time to clear behind as Dunn raced into the six-yard box.
Chances continued from Rovers before the break, Gestede glancing a Tommy Spurr cross just wide, before the striker saw a goal chalked off after he was adjudged to have fouled Almunia in the build-up.
The final opportunity of the half again fell to Rovers, but Almunia saved at his back post as Matt Kilgallon met Craig Conway's corner kick.
It was a strong first half from Rovers who quickly recovered from the disappointment of going behind to dominate proceedings.
Rovers were given a huge let-off straight from the restart as the home side had a goal chalked out for offside.
As the lively Ikechi Anya raced into the box he squared for strike partner Troy Deeney who tapped home from close-range, but the linesman's flag was raised.
Then on 49 minutes the Hornets' pair combined once more to create another excellent chance, this time Deeney the provider for the Scottish international, but his shot across goal flashed wide.
Rovers rode that early second half pressure and slowly got themselves back towards Almunia's goal.
David Dunn tried his luck with an audacious volley from 35-yards that flashed just past the post, then Rudy Gestede headed powerfully wide from yet another Tommy Spurr throw.
Just past the hour mark Rovers took the lead for the first time on the night and it was all down to the intelligent play from David Dunn.
As a Craig Conway free-kick was only punched as far as Dunn by Almunia, the midfielder embarked on a trademark jinking run into the area before laying the ball on a plate for Conway and the Scottish international couldn't miss from ten yards.
It was Conway's third goal since signing for Rovers at the end of January, all of them coming on the road.
Alas Rovers had little time to enjoy their lead as the hosts were handed a way back into the match on 70 minutes.
Live-wire Anya attacked from the left and as he crossed the ball struck Todd Kane a couple of yards away, referee Darren Sheldrake pointing to the penalty spot much to the disdain of the Rovers contingent.
Watford's top scorer Troy Deeney stepped up and made it 2-2, sending Paul Robinson the wrong way with a low shot into the left corner of the goal.
Rovers went back on the attack, looking to regain the lead once more, Matt Kilgallon crossing for Jordan Rhodes but his header was cleared over his bar by Daniel Pudil.
Then the home side were fortunate not to be down to ten men after Gabriele Angella hauled down Jordan Rhodes as he looked to break through. The Hornets' defender had already been carded but somehow escaped receiving a second.
But just as it looked like the match would end with Rovers having all the momentum, Watford struck what seemed a decisive blow on 88 minutes with a goal on the break.
As Watford struggled to clear their lines, substitute Lewis McGugan fed Anay, and with Rovers having committed men forward the ball was played through for Cristian Battocchio who applied the composed finished.
It was tough on Rovers as they had been much the better side.
Rovers were given a boost when six additional minutes were shown, and they took full advantage with a deserved equaliser once more.
They pressed down the flank with Tommy Spurr before Matt Kilgallon floated a ball into the box to where Rudy Gestede rose highest to power a header goalwards that bounced off one post and nestled into the opposite corner of the goal.
A tremendous goal and one that was just reward for another strong display from the big man.
There was still time for more drama as Rovers had a shout for a penalty waved away as substitute Luke Varney looked to be pushed in the box. In the resulting melee Varney himself struck goalwards but Watford somehow hacked clear.
As the final whilst was blown Rovers were delighted to have come from behind to claim a point, but on chances created, it really should have been three.
WATFORD: Almunia (c); Hoban (sub McGugan 72 mins), Angella, Ekstrand; Cassetti, Murray (sub Battocchio 61 mins), Tozser, Merkel (sub Diakite 75 mins), Pudil; Deeney, Anya.
Subs not used: Bond (GK), Doyley, Faraoni, Neill.
Goals: Cassetti 4 mins, Deeney (pen) 71 mins, Battocchio 88 mins.
ROVERS: Robinson; Kane, Keane, Kilgallon, Spurr; Evans, Williamson, Conway, Dunn (sub Varney 90 mins); Gestede, Rhodes.
Subs not used: Eastwood, Hanley, Olsson, Taylor, Feeney, Dabo.
Goals: Dunn 27 mins, Conway 64 mins, Gestede 90+3 mins.
Booked: Evans, Kane, Kilgallon.
Attendance: 13,921 (including 380 Rovers fans).