While the undefeated Bulldogs were hot favourites to be the first side through to the grand final, it took a Zac Taylor try with a tick over three minutes left in extra-time to snatch the win.

Even before then there was drama as the Roos - on the back of an impressive performance from their forward pack in bitterly cold conditions - led 15-8 when the siren sounded.

But Bulldogs were camped inside the Roos' 22 and having earned a penalty, play went on.

More penalties came, Dubbo lost Zarrin Galea to the sin-bin after a yellow card and then Bulldogs' Thomas Felsch charged over from a penalty tap.

Ethan Ivory landed the pressure conversion in the blustery conditions to lock it up at 15-all and trigger two more five-minute periods of extra-time.

"That's really incredible," Shannon Felsch said.

"The conditions didn't really suit us, we are more of a running side. Anyway, what can you say? We showed a lot of ticker.

"That's only the second time we've done it, we also did it against Narromine, came from behind and got the result. I don't know why they believe so much, but yeah, they believe.

"Considering that's my young bloke who scored after the siren and he'd been in a boot, three weeks ago he snapped the ligament in his foot, and he's scored the try there - crazy.

"We'll see Dubbo again, they're a good side."

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The match began in the snow and the rain, with the Roos forced into a positional reshuffle as road closures kept flyhalf Charlie Kempston from making the match.

Bulldogs opened scoring after two minutes via an Ivory penalty goal, and not long after a Roos defensive error - knocking on when trying to clean up a kick - saw the margin increase.

Dougal Murphy had chased hard after the kick and as the ball spilled into the in-goal, he dived on it to help Bulldogs to a 8-0 lead.

But after that it was the Roos who stepped up as they began to dominate possession and in turn, enjoy good field position.

A penalty goal then a nice pick and drive try from Roos skipper Hugh O'Leary saw it locked up at 8-all three minutes out from the break.

In the second half Bulldogs spent the first 10 minutes camped inside the Roos' 22, but the visitors held on. At one stage they repelled eight phases following a Bathurst scrum.

Finally the Roos were able to cart the ball down field and after coming within inches from a scrum, a quick O'Leary penalty tap caught Bulldogs out.

The conversion made it 15-8 with 11 minutes left.

But Bulldogs remarkably levelled it up after the siren and after falling behind 18-15 in the first period of extra-time after a Roos' penalty goal, Taylor steamed on the ball and forced his way over for the match winner.

While the Bulldogs celebrated, Roos tried to find the positives in having come so close to ending their rivals' winning streak.

"This team has been building pretty well in the second half of the year, the coaches have done a good job there, they've come together nice at the right time of year," Dubbo director of coaching Beau Robinson said.

"It is disappointing to lose, obviously we've now got next week to get through and the boys will have to focus on that. But there's a lot to take away from that performance.

"It was a good effort, especially with our disrupted preparation today. Our five-eighth got stuck in Sydney, we couldn't get him back, so our 15 had to play at 10.

"I was really happy with that effort, the boys should get a lot of confidence out of it.

"Bulldogs are a very good team, but when it comes to finals football, anything can happen. That's what's great about finals football and makes it so exciting. Anything can happen."