England goalkeeper Ramsdale had missed the last three games after being dropped for David Raya, but he kept a clean sheet as the Gunners won 1-0.
Reiss Nelson scored the only goal of the game, with Eddie Nketiah pouncing on a poor back-pass from Zanka to tee him up.
Brentford rallied in the second-half and went close to scoring on two occasions, but Arsenal held out to go through.
Simon Collings was at the Gtech Stadium to see Arsenal in action...
Aaron Ramsdale 8 | Star player
Back in the team after being on the bench for the previous three matches. Had a good game, with his distribution impressive. Made a huge save to deny Yoane Wissa in the second-half.
Ben White 6
A fairly solid performance from the right-back. Did not seem to get forward as much as he usually does, perhaps because he had a young debutant ahead of him.
Takehiro Tomiyasu 8
Regularly plays centre-back for Japan, but this was his first start there for Arsenal. Did well, making a few vital blocks in each half. Finished the game at right-back.
Imposed himself well on Brentford’s strikers and kept them largely quiet. Did not seemed fazed by playing with a new centre-back partner.
Jakub Kiwior 8
Looked really assured at left-back. Has come a long way from when he joined the Gunners in January. Even filled in at centre-back for the final 20 minutes, making a heroic block to clear Keane Lewis-Potter’s shot off the line.
Emile Smith Rowe 7
Made his first start in 499 days and his 100th appearance for Arsenal. Looked sharp at times with some lovely darting runs. Faded towards the end, which is understandable given his lack of minutes.
Had a nightmare game against Tottenham on Sunday when he came off the bench, but recovered well here. Largely unflappable when in possession.
Kai Havertz 6
Another frustrating night for the German, who is yet to get going at Arsenal. Made some important defensive contributions, but looked off the pace in attack.
Charles Sagoe Jr 6
The 19-year-old was handed his debut in a surprise call by Arteta. Put in a solid shift before being taken off with around 20 minutes to go.
Eddie Nketiah 7
As ever, he worked tirelessly up top for the team. Showed composure to setup Nelson when he pounced on a loose pass by Zanka.
Reiss Nelson 7
Took his goal well by calmly finding the bottom corner. Worked exceptionally hard off the ball for the team, too. If Gabriel Martinelli and Leandro Trossard aren’t fit this weekend, he could start.
Oleksandr Zinchenko (White 68’) 6
Came on and brought some control to Arsenal when they were rocking.
Gabriel Jesus (Sagoe Jr 68’) 6
Once again tasked with playing out wide. Did fine during this little cameo.
Martin Odegaard (Smith Rowe 82’) N/A
Mohamed Elneny (Nelson 82’) N/A
Cedric (Nketiah 87’) N/A
Subs not used: Hein, Sweet, Walters, Cozier-Duberry.