The Reds had been 2-0 ahead at halftime before Wolves fought back after Matheus Cunha scored, which had the hosts clinging on at the end.
Robertson later said: "Yeah, we just managed to dig deep.
“Obviously 2-0 at half-time, we know that can be one of the most dangerous results in football. We had to come out and we had to start well – and we didn’t quite do that.
“I think the second half was a slog, maybe playing on Wednesday has taken it out of a few of the lads or whatever. But it was all about trying to use the experience we have got on the pitch, trying to use everything that we’ve got. And I thought we dug deep.
“When they scored, everyone gets nervous. The players get nervous, the crowd get nervous – of course that’s only natural. But it’s a massive win for us and another game down.”