Late goals from Lyndon Dykes and Kenny McLean snatched victory from the jaws of defeat in Norway, and have Scotland top of their group on a maximum nine points.
A home win against Georgia on Tuesday would bring Euro 2024 tantalisingly close, and earn a fourth straight qualifying win for the first time ever.
"We couldn't have started this campaign better," Robertson told Viaplay.
"We have to qualify now. The lads who came off the bench did so well. Going behind is difficult, but we knew this was the next step in our improvement.
"It was trying to get the balance right. The team spirit is second to none. To create that in international football is unique."
For 85 minutes, Scotland had performed below the high standards they set in beating Spain at Hampden, and trailed to Erling Haaland's penalty.
Clarke's side had only had two shots and did not look like mustering much more in heat of more than 30C. They had defended fairly well, but the melting conditions and long season seemed to be taking their toll.
But then came McLean off the bench, much to the frustration of many on social media who felt bringing on a defensive midfielder was not exactly what was needed, and it all changed.
He scored a wonderful winner with his weaker foot, and combined with Dykes and McGinn brilliantly.
Dykes was also drawing criticism after a quiet game, but he and McLean epitomise Clarke's Scotland. Loyalty to players, which brings togetherness and maximum effort, and both repaid their manager in spades.
"The lads did so much, and we made the changes and got some momentum after the first goal," McLean told BBC Scotland.
"Goals change games and they did for us. We were hanging in at the end. The lads who played 90 minutes out there, I don't know how they did it. I was sat in the dugout sweating. Just watching it I was knackered.
"We've worked so hard over the last few weeks, results like this make it worth while. We're in a decent position, but we want to be in an even better position."
Those pivotal five minutes - from when Haaland went off to Scotland scoring twice - now have the usually cautious Tartan Army scrambling for flights to Germany for the Euros.
There is plenty of work to do, however, with return games against Spain and Norway to come and, firstly, Georgia on Tuesday.
"Looking at the live table - I don't want to jinx it - but I can't see a way that we're not in Germany," former Scotland striker Steven Thompson said on Sportsound. "I just can't see it.
"The belief that we have in the team is so important. If we win on Tuesday, all bets are off for me."
A win against Georgia, far from certain given Scotland's recent record against them, would also put pressure on Spain in the race to top the group.
"Those two minutes have turned the whole game around," said former Scotland defender Willie Miller."You can now be positive, and it's a brilliant place to be positive sitting top of the group with nine points. Dare I say it, they're now looking at the possibility of topping the group."