The Norwegian midfielder grew accustomed to his countryman's methods at former club Stromsgodset, prior to effectively forming the advance party to Parkhead for the man whose parting gift was to steer the Gulskogen-based outfit to its first league title in 43 years.
But anyone expecting him to receive special treatment this summer should think again. For Deila, who transformed Johansen from a free transfer from Bodo/Glimt to a million-pound-plus Norwegian international, knows exactly what this 23-year-old can do and isn't prepared to accept anything less.
Indeed. he has challenged Johansen to raise his game in the fluid, short passing, pressing system he has begun to implement within the Scottish champions. Located on Tuesday night alongside new captain Charlie Mulgrew at the base of Celtic's midfield, more specifically he has been instructed to be quicker in possession and stronger on the ball.
"There is a big difference between how this team plays and how we used to play in Norway," said Johansen. "I don't want to say bad things about Stromsgodset, but the quality of the players is much higher here. But the philosophy is the same. Ronny tries to do the same things. We like to build from the back. That's what the manager likes and we will adapt more as we go on.
"He has spoken to all the players about what he expects from us. He has told me what I can improve on and be better at.
"What can I improve on? Maybe be a bit stronger in the tackle," he addded.
The Norwegian perhaps took that diktat a little too literally when he appeared to aim an elbow at an opponent in the club's 4-0 second leg qualifying win over KR Reykjavik at Murrayfield on Tuesday night. It was the kind of scrape which Scott Brown, in whose injury-enforced absence he will be relied upon more than ever, often finds himself.
More than anything Brown's two-month injury lay-off means the unfolding of another chapter in the narrative of Mulgrew.
Eight years on from leaving the club as a makeweight in the deal which took Lee Naylor from Wolves to Celtic, the 28-year-old's reinvention was complete when he acquired the captain's armband. Johansen was delighted with the decision.
"I love to play with Charlie, he's a great footballer," said Johansen. "It's easy to play with guys of his ability. You never want to lose players like Broony - he means a lot to the team. But when he is out, someone else needs to take charge. Charlie is the captain now and he does the job well."
The Icelandic element, of course, was merely the first part of the club's qualifying equation. Next Wednesday's assignment is markedly more difficult, as they travel to Warsaw to take on Polish champions Legia. With former Norway, Blackburn, Manchester United and Rangers centre-half Henning Berg at the helm, they are another team with a Norwegian connection to speak of.
No Polish side has made it to the Champions League group stages in 18 years, but Johansen is well aware that the Ekstralasa champions - 6-1 aggregate winners against St Patrick's Athletic - will provide quite a step-up. Goalkeeper Dusan Kuciak is highly regarded, while Marek Saganowski has experience and pedigree going forward.
Johansen said: "We know the next round will be tougher than Reykjavik. It will get harder as we progress. That's the Champions League and that's the way it should be. If you want to be with the best, you have to beat the best."