Jurgen Klopp's side produced a statement win at Ibrox on Wednesday following a difficult start to the domestic campaign that has left them in 10th place after eight games, 14 points off leaders Arsenal.
Robertson, who made his first appearance in over a month at Rangers after recovering from an ankle injury, said Liverpool will need the same intensity against City, who are second.
"We need to try and get consistency back into our game, into our performances. That's what we have been lacking this season... we have to keep that going, we have to play with that intensity," the Scot told reporters.
"(City) are a fantastic side and they are flying at the minute. It will be difficult to play against them but us at our best we can always compete. Anything below that and it will be a difficult afternoon."
Robertson was full of praise for forward Mohamed Salah (30) after he came off the bench to score a stunning six-minute hat-trick against Rangers, the fastest in Champions League history.
Salah has looked a pale shadow of himself this season, netting just twice in the league, but Robertson said this could be a turning point for the Egyptian.
"That's what he can do. You give Mo chances and he will score goals. So that will give him loads of confidence from that. He's a fantastic, unbelievable player," he added.
"Obviously he came on and wanted to get his name on the scoresheet. Luckily he's managed to get three."
