The striker has struggled for form and regular minutes since his arrival at Goodison Park last summer.
The Venezuela international fired a second-half double to move Everton into the quarter-finals of the historic competition at Goodison Park.
Lampard insists Rondon offers the Blues a different option up top to Dominic Calvert-Lewin and Richarlison - which could be important in the bid for top-flight survival.
And the the Everton boss feels the centre-forward has been hitting the levels that made him a fans’ favourite at Newcastle United during training.
When asked if Rondon could get back to the form he displayed at St James’ Park, Lampard replied: “To me he has - in terms of his personal levels of training.
“When I came in, he was slightly delayed. He was in for the first few days for different reasons.
“Every day he has trained, he has trained really well. To train as a striker when you’re not starting, it’s not easy.
“You have to keep sharp and he’s done that every day in training. In that sense, he’s been an ideal squad member with his attitude.
“When he comes in, and he comes in today, he contributes and he gives us something different.“
“He’s a different style of striker for us. A good, physical presence in the box and we need that. We need that for the squad ongoing.”