And on-loan Tottenham star Keane believes they have already formed an understanding in their short time playing alongside each other.
Indeed, four of Keane's five Celtic goals have been scored when Rasmussen has been on the field.
"He's very good," Keane told Celtic View.
"He's only 25 and still learning the game. He's a young lad but I've been impressed so far with what I've seen.
"I played with him in the second half of the Dunfermline game when I scored the penalty and I think we did really well together.
"We linked up quite well and he was the one who put me through to get the spot-kick.
"He's strong and, although he's not overly-tall, he's not small either. He's very good in the air so I think he has a good future ahead of him.
"And he's obviously a goalscorer, he plays very high up, plays on the shoulders of defenders and links play well."
Keane has also reopened the debate over the state of Falkirk's pitch by claiming "it's not good for the game".
It is understood Celtic expressed concerns about the condition of the Bairns' playing surface to the SPL ahead of Sunday's match, though manager Tony Mowbray categorically denied this.
The Hoops' alleged intervention angered Falkirk and Keane's comments are unlikely to please them either.
"I don't think many people are used to playing on pitches like that," he said.
"I've been watching it (Scottish football) as an outsider for the last few years and I can't recall the pitches being that bad.
"I don't think the standard of the pitches - thanks to the weather - have helped the league. It's not good for the game."
Meanwhile, Mowbray has revealed Marc-Antoine Fortune is the only one of his injury concerns likely to be available for Saturday's Scottish Cup quarter-final at Kilmarnock.
He aid: "We have been pretty hopeful with Glenn Loovens over the last few weeks and he has trained both days before the games but woke up the following day and not felt right, so let's wait and see.
"I think Jos Hooiveld would hope to start training this week, but he has probably been out too long to come straight back in.
"Shaun Maloney, I think, is going to start training this week, too.
"However, I think he falls into that same category.
"I imagine Marc-Antoine Fortune will train this week as he had a dead leg rather than a bad strain or tear.
"Niall McGinn and Paddy McCourt, meanwhile, might be another week or so, and Diomansy Kamara and Thomas Rogne are out for a few weeks as well.
"So it might just be Fortune who has a chance for this weekend."
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