The 26-year-old midfielder has been brilliant in Euro 2016 as surprise package Wales gear up for a semi-final with Portugal tonight.
His form in France is unlikely to surprise Liverpool fans after the way in which Allen improved since Jurgen Klopp replaced axed Rodgers back in October.
The Northern Irishman managed Allen at Swansea and then shelled out £16 million to bring the midfielder to Liverpool back in 2012.
Rodgers, in fact, worked with a lot of the current Wales side during his successful stint with the Swans, and the Celtic boss is delighted for all of them - but especially the "top class" midfielder.
“I’m obviously pleased for a lot of the players that I’ve worked with," he said via The Daily Record.
"I’ve always said that Ashley Williams is a top-class centre half. Neil Taylor was a young boy who came in from Wrexham, and he did great. Ben Davies as well.
"And Joe Allen, I’ve always said, is a top class midfield player, and is starting to show it."
Rodgers, whose was appointed Celtic boss in May, has been linked with another move for Allen - whose contract expires next summer - but he might have better offers on the table following his exploits in France.