Deila left Scottish Premiership giants at the end of last season after two years in charge.
Former Liverpool and Swansea City boss Rodgers has been appointed as the new manager of the Bhoys.
Ajer signed a four-year contract with Celtic in February, as announced on the club’s official website at the time.
The 18-year-old Norway Under-21 international midfielder is set to join his new Celtic teammates this month.
The youngster has revealed what his Norwegian compatriot Deila told him about Rodgers.
Ajer has also suggested that he knew that Deila might not be in charge of Celtic for the 2016-17 campaign when he signed his contract with the Glasgow giants in February.
"I knew that Ronny might not be here when I came in but then I saw Brendan Rodgers had been appointed, and what he brings with him made me really excited,” Ajer told Celtic’s official website.
“Ronny spoke to me when Brendan was appointed and he wished me good luck and he told me Brendan was a good manager.
“Ronny has always been a great manager and I just wished him good luck and hopefully we will meet again at some point.”
Ajer is a talented young player, and he will be determined to impress Rodgers during pre-season.
The 18-year-old Norwegian midfielder is unlikely to establish himself in the Celtic first team rightaway, but he could be given chances as the 2016-17 campaign progresses.