Forrest is playing well for Celtic at the moment, and the 27-year-old winger has established himself as an important player in Brendan Rodgers’s side.
Roberts, spent two-and-a-half years on loan at Celtic from Premier League giants City from January 2016 until the end of the 2017-18 campaign, has spoken highly of Forrest.
The former England Under-20 international winger - who joined City from Fulham in the summer of 2015 for an initial transfer fee reported by The Sun to be worth £4 million - has also backed Celtic to win the Scottish Premiership title this season.
Roberts told The Scottish Sun: “Jamesy is a top talent and so consistent.”
The winger added about the title race: “I don’t see anyone stopping Celtic this year. I know other teams have stepped up, but Celtic are now kicking into good form. They are still too strong for the rest.”
Roberts was hugely successful during his time at Celtic, as the winger won won the Scottish Premiership title three times, and the Scottish League Cup and the Scottish Cup twice each.
According to The Sun, Roberts will consider leaving City permanently at the end of the season when his loan spell at Girona runs out.
The British tabloid has claimed that Celtic would lead the chase for the 21-year-old next summer, and that Leicester City want the youngster as well.