Fetalaiga Pauga was sent off for an ugly high shot on Bulldogs fullback Connor Tracey in the last eight minutes and the Roosters were then reduced to 11 men after Walker pulled a professional foul.
But their lead never looked under threat despite the late casualties, the side confirming victory at a rainy Central Coast Stadium even without their four State of Origin representatives.
"We're on the improve," said Roosters coach Trent Robinson.
"I feel like we know where we're headed, we're really clear on our game. We're heading in the right direction."
Despite a breakout game from ex-rugby sevens star Jeral Skelton, the Bulldogs struggled for consistent opportunities, in no small part due to their poor ball-handling in the wet.
Across the first 75 minutes of Saturday night's game, Canterbury enjoyed only two tackles in the Roosters' 20.
"We probably missed an opportunity there to climb up the leaderboard a little but I'm incredibly proud of how gritty and how much effort they put in," said Bulldogs coach Cameron Ciraldo.
"(But) we obviously didn't play the conditions as well as they did."
Nat Butcher was one to profit from Sam Walker's class in the rain. (Dan Himbrechts/AAP PHOTOS)
The Tricolours had no shortage of chances, Walker setting up all four of their tries.
In the first half, he threw the last pass to Dom Young that helped Easts to their first try from a scrum play, then threaded a kick through the line for Nat Butcher.
When Skelton spilt the ball during the first set after halftime, the visitors were in position to extend their lead through and Walker kicked for Terrell May - immense with 213 run metres.
Looking to bounce back from his Origin omission, Canterbury's Matt Burton struggled to exert his usual influence after being shifted to centre as Bronson Xerri's injury replacement.
He missed a tackle on Joey Manu that allowed the Roosters to march up-field for their fourth try, scored by Blake Steep after yet another pinpoint pass from Walker in the final 15 minutes.
"It was a really good night for (Walker) but he had to make those choices," Robinson said.
"He was outstanding."
Steep's got his first — NRL (@NRL) #NRL 🥧 #NRLRoostersBulldogs pic.twitter.com/2c6rKCCyv6June 22, 2024
Axed for last week's game for missing the Roosters' mid-season review, Brandon Smith kicked a crisp 40/20 that put his side in position for its second try and a 14-4 halftime lead.
The hooker was busy out of dummy-half, running for 77 metres in the first half before having his minutes curtailed in the second 40.
In his first NRL game this year, Bulldogs winger Skelton came up with a contender for tackle of the year, jamming in to absolutely flatten a sore and sorry Pauga in the first half.
He had a hand in both the Dogs' tries, first tearing away to put Jaeman Salmon over on the right edge, and then dashing away for a length-of-the-field effort.
Pauga looks certain to spend time suspended for the shot that ended Tracey's night.
"He's not well," Ciraldo said of the fullback's condition.
Pauga could be joined on the charge sheet by Walker, who hit Jacob Kiraz with a far milder high shot early on.
In an amusing subplot, referee Grant Atkins needed to stop play in the first half after finding a mobile phone on the turf, presumably left behind by a pitch invader who had rushed the field earlier.
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