The Reds booked their place in the knockout stages with a 2-0 victory in Austria.
Speaking to BT Sport, Robertson said: "Mo missed a couple of great chances. He and Bobby put so much pressure on themselves to score.
"We kept saying 'the next one, the next one, the next one', then he goes and scores from a ridiculous angle. I don't know how he's got it in from there on his weaker foot.
"All round it was an excellent team performance. People were saying that we were struggling, but we finished with four points more than last year and topped the group. We have got into the last 16 and know what we can do from there."