The former Celtic assistant manager made the claim in the aftermath of the club’s 2-0 victory over Hearts, which confirmed their unbeaten Ladbrokes Premiership season.
Roberts will return to Manchester City this summer after his 18-month loan deal at Parkhead expires, though there have been reports that Celtic have made a £6.8m bid for the player.
City boss Pep Guardiola has indicated he’ll judge Roberts in the summer and whether he’s worthy of a place in the first-team squad at the Etihad next term.
Collins insists the player is good enough for a regular spot in the City squad, believing him to already be better than England international Sterling.
He said on Sky Sports: “I think he’ll go back to Manchester City. I think he’s better than Raheem Sterling, who cost £50million. I think he [Roberts] scores goals.
“I’d love him to stay at Celtic and entertain the Celtic fans, but I think he’ll return.”