Rangers loaned out the 18-year-old winger to Inverness last summer for the first half of the season and he made an impact with the Scottish Championship club.
Ahead of signing Kennedy, Robertson conceded that the club were warned about the youngster’s attitude and his ego, which could have been disruptive inside the dressing room.
But the Inverness manager stressed that the youngster was nothing like what he heard about him before he arrived and insisted that he was one of the hardest-working players in training and was prepared to listen to any sort of advice without any questions.
Robertson admitted that he is not sure where Kennedy earned a bad reputation as he is completely different in real life.
“We kept being told by one or two people that you’ve taken a handful there”, Robertson told The Athletic.
“That he’s got a bit of an ego, he thinks he’s better than he is, he’s a bit of a prima donna.
“Not the case in any way, shape or form.
“He was really hard-working, listened to what we said and did his best to please us in terms of his duties; never questioned anything, he was always there ready to go.
“It’s amazing how someone can get a reputation.”
Kennedy left Inverness earlier in the month and Rangers loaned him out to Raith Rovers for the rest of the season.