BRENDAN Rodgers may find persuading the Celtic board to part with the sizeable sums of money it will take to bring in the quality players he wants a little easier after this nerve-wracking evening.

A 3-1 aggregate victory, secured after they had ground out a 0-0 draw, on paper at least, may well have been an improvement on the 1-0 triumph they recorded against the same opposition at the same stage of this competition 12 months ago.

Yet, the Scottish champions had the poor finishing of their Norwegian counterparts and the goalkeeping of Craig Gordon, who pulled off vital saves in either half, to thank for their safe progress.

Read more: Brendan Rodgers hails Kris Ajer and Jack Hendry as Celtic withstand Rosenborg barrage to progress in Champions League​

It could very easily have been a different story. At certain points it looked as if an ignominious exit was possible. It was difficult viewing for the travelling support.

Their team certainly deserved credit for how they defended and for keeping a clean sheet. But there will have to be a stark improvement in performance if AEK Athens of Greece, who they will face at Parkhead next Wednesday evening, are to be overcome and a play-off place clinched.

The absence of key first team regulars like Dedryck Boyata and Mikael Lustig, who have just returned to training having represented their countries in the World Cup, and Jozo Simunovic, who was suspended after being ordered off in the previous round, was keenly felt.

However, Rodgers, who has brought in Odsonne Edouard from Paris Saint-Germain for a club record £9 million fee this summer, would be more confident of maintaining their domestic and European success in the months ahead with a few more new faces and this fraught outing illustrated exactly why.

Rodgers fielded exactly the same starting line-up as he had in the first leg. That meant Kristoffer Ajer and Jack Hendry renewed their partnership in the centre of his defence.

Read more: Five things we learned as Celtic beat Rosenborg to set up AEK Athens test​

The youngsters had, after a shaky start, done well seven days earlier in direct opposition to Nicklas Bentdner. But playing away in Europe is a different proposition altogether. They endured a torrid 90 minutes and will learn from the experience.

The disarray that Rosenborg are in off the park – the surprise sacking of their popular and successful manager Kare Ingebrigsten last month shocked fans and prompted to players to issue a public appeal for his reinstatement – aided the visitors’ cause.

That the Lerkendal Stadium was far from a sell-out showed what most Rosenborg fans thought about their chances of progressing. It had been full to its 21,405 capacity last season. But those home supporters who did turn up had plenty to cheer about.

Rini Coolen, who has taken over from Ingebrigsten on an interim basis, made one change to his side. He brought in Alexander Soderlund for Jonathan Levi. Coolen was interviewed on the pitch before kick-off and admitted his men would go on the offensive. He was true to his word.

Cristian Gamboa, a former Rosenborg player, retained his place at right back ahead of Lustig. The Costa Rican did well to dispossess Pal Andre Helland as the winger advanced towards the Celtic goal in the eighth minute.

Read more: Brendan Rodgers hails Kris Ajer and Jack Hendry as Celtic withstand Rosenborg barrage to progress in Champions League​

Thereafter, however, Gamboa often struggled to deal with the onslaught his team was subjected to. He was not the only one of his team mates who that could be said about.

Celtic offered next to nothing going forward in the first-half and failed to get a single shot on target. Andre Hansen in the Rosenbog goal was hardly tested all night.

The hosts dominated possession and were unfortunate not to pull a goal back in the first 45 minutes. The failure by Gordon and Hendry to deal with a Helland cross into their six yard box in the 16th minute caused unnecessary alarm. It set the tone for much of what was to follow.

Soderland volleyed wide in the Celtic goal after being supplied by Marius Lundemo four minutes later. The Rosenborg players appealed for a penalty shortly after that when Birger Meling went to ground following a challenge by Hendry. Sandro Scharer, the Swiss referee, was unimpressed by their protests.

Tore Reginiussen fired narrowly past the right post and Lundemo had a header tipped over by Gordon. The Rosenborg players must have wondered how they had failed to net as they left the field at half-time.

Celtic started the second-half positively when Callum McGregor unleashed Odsonne Edouard down the left flank. The French striker, the scorer of two goals in the first leg, used his pace and physique to force his way past Vegar Hedenstad, but his attempt just missed its intended target.

Read more: Five things we learned as Celtic beat Rosenborg to set up AEK Athens test​

The Glasgow club managed their first shot on goal in the 54th minute after Ajer and Sinclair combined to set up Olivier Ntcham. But his long-range effort lacked power and was easily dealt with by Hansen.

Rodgers withdrew James Forrest, who had worked hard to carve out an opening despite receiving limited service and put on Tom Rogic in the 63rd. The playmaker took up his favoured position just off lone striker Edouard and McGregor moved out wide.

Levi, who had just come on for Anders Trondsen, nearly netted almost immediately. He cut in from the right side and whipped a shot that Gordon had to show superb reactions to deny.

Rosenborg finally managed to get the ball in the net with three minutes remaining, but Scharer ruled that Reginiussen had fouled Gordon before he had nodded in from a few yards out.