The winger is on loan with the Scottish Premiership side from Manchester City.
The 19-year-old is on loan with the Hoops until the end of next season, but has already shown during the first few months of his time with the club that he has the potential to be a very special talent.
And Magath - who handed the winger his professional debut when the pair were at Fulham - explained why the decision to join the Bhoys was the right one.
"Celtic are a good club for him to continue his education," he told The Scottish Sun.
"They are dominant in Scotland and for an offensive player I think it is always good to be part of an attacking side.
"Playing in Europe is a bonus at this stage of his career but he has everything required to succeed at the top level."
Though Roberts' ability was obvious from his first couple of appearances for Celtic, it was the clash with Hearts at the start of April that confirmed that he was able to back up his skill with end product as he bagged a brace to help Ronny Deila's men to a 3-1 win.
And after his character was severely tested following an incredible miss in the Old Firm Scottish Cup semi-final, he proved that he had the temperament to bounce back as he scored four times in the final four games, including a brace in the win over Aberdeen that clinched the title.
And he will hoping that he can continue that form next term to prove to his parent club that he has the potential to make an impact the Etihad.