Boss Brendan Rodgers described Celtic's performance as "sensational" after James Forrest's second-half strike gave the Hoops a 1-0 win over Rosenborg and took them another step towards Champions League football.
Following the goalless draw at Parkhead last week, the Scottish champions again started without their only two recognised centre forwards Moussa Dembele and Leigh Griffiths - the latter came off the bench in tension-filled Trondheim after recovering from a calf injury - with winger Forrest asked to move into the middle.
The Scotland international was thwarted in the first half in the Lerkendal Stadion but in the 69th minute, he fired high past keeper Andre Hansen to take the Parkhead club into tomorrow's play-off draw with a 1-0 aggregate win.
Celtic had to cope with the absence of defender Erik Sviatchenko, who returned from injury but hobbled off in the 25th minute to be replaced by midfielder Nir Bitton.
Ulsterman Rodgers said: "It was a big performance. Take away the win, what was important for me was the maturity.
"This time last year I was going into these games with a hope that we could go through, to try to find a way.
"To come out here and play to that level with that composure - everyone was talking about the pressure of the game, so to play that way was sensational, really.
"I am really delighted with the players, how they managed the game, how they kept their nerve and courage to play. Yes, it was a great victory for us."
Rodgers further detailed his delight by saying: "Look at Nir Bitton tonight, coming into the game as a midfielder.
"I always love a midfielder who can play at centre-half and he came in and played as if he had played there all his life.
"(He showed) great composure, defended well and took the ball under pressure which we expect from him.
"So players filling in from different positions... James Forrest got his goal from wide but did a great job centrally. He should have scored another one but I think he played the role really well.
"It was a brilliant goal. It is a huge credit to players and where they are at now in their development."
Celtic will face either Qarabag, Astana, Rijeka, Slavia Prague or Hapoel Beer Sheva in the play-off.
"When the draw comes it is going to be one of those anxious moments again at some point over the two legs," said former Swansea and Liverpool boss Rodgers.
"But like I say, 12 months on it is a different mentality and feel.
"The squad are happy to go through but as I said I now expect that and that comes from the belief of how they work and how they play.
"Whoever we get it will be a tough game and my focus now will be on Hearts on Saturday."
Rosenborg manager Kare Ingebrigtsen claimed his side paid the price for not taking their chances in the first game at Parkhead.
He said: "We gave Celtic too much respect in the first 45 minutes, in the last 45 minutes we handled them much better.
"We put some pressure on them but in the best period of our game they scored a goal, it was a clinical finish.
"Over two legs it was small margins. We should have scored in Glasgow, that's where we lost it, not today."
ROSENBORG: Hansen, Hedenstad, Bjordal, Skjelvik, Meling; Jensen, Konradsen, Midtsjo, Jevtovic (Helland, 73 mins), De Lanlay (Vilhjalmsson, 73 mins), Bendtner. Unused subs: Ostbo, Rasmussen, Rashani, Gersbach, Lundemo.
CELTIC: Gordon, Lustig, Simunovic, Sviatchenko (Bitton, 25 mins), Tierney, Brown, Armstrong (Rogic, 71 mins), Hayes (Griffiths, 57 mins), McGregor Sinclair, Forrest. Unused subs: de Vries, Gamboa, Kouassi, Ntcham
Referee: Jonathan Lardot (Belgium)
Man of match: Jozo Simunovic Match rating: 6/10