The 22-year-old set up Tommy Rowe's 83rd-minute equaliser as the visitors came from behind to take a point at St Andrew's
Indeed Palmer was at the heart of most of the Robins' best attacking play, twice setting up fellow new-boy Benik Afobe with convertible chances.
Lukas Jutkiewicz put the hosts ahead in the 63rd minute when Marc Roberts recycled a clearance from a set-piece and lifted a cross to the back post.
Jutkiewicz was on hand to underline his aerial dominance by powering a header past Daniel Bentley for his opening goal of the campaign.
But with seven minutes left Rowe, a free transfer from Doncaster, smashed Palmer's inviting pass across Lee Camp and into the far corner.
It was no more than the Robins deserved after Afobe twice went clear only to be denied by Camp.
"First and foremost I am most pleased that Kasey got 90 minutes," Johnson said.
"That is his first 90 minutes probably in about 18 months, for him to get through that is a big tick in the box and credit to him in terms of the fitness work that he and we have done with him.
"To have him back and fit is great providing, like he did today, a lot of goals and assists. He played two or three passes that Glenn Hoddle would have been proud of.
"I thought we had the exceptional chances in the match. I was pleased, it has given us something to build on both in terms of performance and result.
"I always want to win, of course, but at the same time when you make late signings in the window and lose key players for whatever reason, it is important that you try and gel and forged that bond.
Blues also had their opportunities with Robins goalkeeper Bentley frustrating the inventive Fran Villalba in the eighth minute and Jutkiewicz just before the hour.
It was Villalba who stood out for the home team, creating in an advanced midfield role, just a few days after arriving on a free transfer from Valencia.
The 21-year-old had just two training sessions before slotting into an unfamiliar team and earned the praise of caretaker head coach Pep Clotet.
He said: "He was very good because he understood very well what we were asking of him, develop a defensive role on that wing but also to link and try to transform what we are going to create in the midfield.
"It was tough for him being at home in front of our fans, I think you can always be a little bit nervous but he took the game forward.
"He is the kind of footballer that can create in tight areas and when the area is at its tightest he is most dangerous because he can think very quick.
"There were a lot of positives today, unfortunately not the most important positive – taking the three points.
"But I think we played a very serious game against one of the most difficult teams we played against last season.
"We played front foot and played a little bit of the football we would like to play, it is very encouraging for the players, they really broke the mould in their bravery today."