But the coach questioned whether the bunker had been consistent in applying its rules after a similar play went unpunished in the lead-up to a Penrith try on Thursday night.

Joey Manu appeared to have scored the Roosters' first four-pointer after he charged through opposite centre Taylan May to plant the ball on the Allianz Stadium turf.

But the bunker spotted Roosters prop Jared Waerea-Hargreaves collecting Penrith's Dylan Edwards as he followed through on a decoy run and rescinded the try.

The Roosters dropped back to 12-0, their momentum stifled.

The call eventually proved significant in the outcome of the game as the Panthers held their fast-finishing hosts off for a six-point win.

It was also brought into sharper focus when Penrith's Liam Martin collided with two Roosters in the lead-up to a Sunia Turuva four-pointer in the second half, only for that try to stand.

Martin bounced between Sitili Tupouniua and Luke Keary, with the first Rooster falling to the turf and the second having his run impacted in attempting to reach the play.

"(The Manu no try) is a bit like how Sitili got knocked over in our one," Robinson said.

"Was he going to save the try? No, he wasn't.

"I don't think (Edwards) would've got there either on Joey Manu. But anyway."

The issue as Robinson saw it was that the first call had applied the obstruction rule to the letter, while the second had used discretion to determine the Roosters' defenders were unlikely to have made it to Turuva and save a try.

"What was the judgement on, I guess is what we're asking," Robnson said.

"Is it, was Luke or Sitili going to get there, or was Edwards going to get there? Or is it the rule on the obstruction?

"I feel like there was two different rulings in that case. One was given, 'Yeah, it's an obstruction but we think it would've got one' and the other one didn't get the benefit of the doubt."

Roosters captain James Tedesco was frustrated by the call, claiming a player who appealed for a penalty would be likelier to secure one.

"He knocked him a little bit to affect him on that. If Keary went to the ground, it probably would've been no try," he said.

Robinson conceded the call was crucial, but would not blame it for the Roosters' defeat.

Easts struggled to wrestle ascendancy back from their fast-starting visitors, ruing first-half errors that kept them on the back foot.

"It was a pretty big play for us but in the end they were a better team by far," Robinson said.

Asked for his opinion, Panthers coach Ivan Cleary said he'd made a pledge with himself not to weigh in on bunker matters this season.

"I'm going to keep that going tonight," he said.

"I'll say one thing, every time we've ever done a black-and-white interpretation in rugby league, it's been a failure.

"I'm not saying that was the case tonight, I'm not saying yes or no, but every time we have, it doesn't work."

Australian Associated Press