Steve Clarke’s squad lost 2-0 against Denmark in Copenhagen to slip to fourth place in Group F.
Robertson was left to lament the concession of two rapid fire goals early in the first half as Scotland were caught cold by the Danes.
“Unfortunately, we weren’t good enough to get anything tonight,” said Robertson. “None of us got passes in the first half.
“The second half was a lot better and something we can build on. We need to do that from the start in the next two games, we can’t give people 45 minutes head start against us.
“It’s really disappointing, the way we played the first half. We knew Denmark were going to come out and get a lift from their crowd.
“We had to weather the storm and I don’t think we did that well enough. We weren’t brave enough on the ball, our distribution from the back wasn’t quite good enough and we couldn’t keep it.
“We kept inviting pressure and when you do that, you need to keep it out of the net. We had a crazy few minutes where we conceded two goals.
“Unfortunately, against a really good team, that’s usually where the game ends.
“But we were determined not to concede any more in the second half and build ourselves into the game.
“I thought we did that and started to get the ball down and start playing. We had a great chance with Ryan (Fraser) in the last 10 which would have made it interesting but it was a top quality save from a top quality ‘keeper.”
Liverpool left-back Robertson had no issues with his unusual deployment as a right wing-back in the first half.
“The gaffer asked me to do a job there and I’ll sacrifice for this squad every time,” he said. “I’ll do it again and again, no problem.
“Of course I’m more comfortable on the left, you saw that in the second half.”