Ramsdale had been Arsenal's first choice in goal since joining in 2021 and played all 38 Premier League games last season, but he was benched for the last three games in favour of David Raya, who arrived on loan from Brentford in August.
On Wednesday, Ramsdale made a crucial second-half save from Yoane Wissa and also denied Frank Onyeka late in the contest as Brentford put Arsenal under heavy pressure, after Reiss Nelson had scored the decisive goal in the eighth minute.
"He's been exceptional around the place with the situation," Arteta said. "We love him more for sure. We know him, we know his character and we are really happy to have him.
"I don't think I'm the one to answer the question about Aaron Ramsdale's quality because I'm the one who signed him when everyone else was questioning that decision.
"Every player is very important. We have a lot of injuries as well and players who contributed. But in football it's about now, it's about the moment. Today, he had the opportunity to play and he played a really big game."
Arsenal will travel to West Ham United in the week commencing October 30 for a place in the quarter-finals.