Roma's 5-1 rout of CSKA Moscow in their Group E opener, coupled with City's defeat to Bayern Munich, has left Manuel Pellegrini's side desperately needing three points
Mancini is currently without a club having departed Galatasaray at the end of last season -- and that has given the former City boss time to keep a close eye on football in England and Italy
"The key (for Roma) is to counter quickly and seize any chances City might offer
Roma need to be vigilant in defence, keep focus for the full 90 minutes and be clinical in attack," Mancini told Monday's edition of sports daily Gazzetta dello Sport.
"A full-strength Roma can beat City, but the absences of (Daniele) De Rossi, (Leandro) Castan and (Davide) Astori could make them more vulnerable."
Roma will likely be without Italy midfielder De Rossi due to a torn calf muscle, while Astori and Castan are still recovering from injury.
Exciting Roma forward Juan Iturbe, meanwhile, has been named in Rudi Garcia's squad for Tuesday's game, suggesting he has recovered from a thigh knock and will play a part at some stage.
Mancini added: "I see Iturbe has made the squad: he can give City problems
On the counter he can be quite devastating."
The Italian, meanwhile, admitted he still feels very close to the club he led to Champions League qualification and the FA Cup in his first full season in charge, and the club's first league title in 44 years the following season.
"I still feel City is a part of me," added Mancini
"City's strong point is the players with whom I won three titles: Yaya Toure, Zabaleta, Aguero, Dzeko, Silva
"I have fond memories of almost all the players I worked with at City."
Manchester was the scene of one of Roma's greatest humiliations -- a 7-1 demolition by City's cross-town rivals Manchester United in the Champions League quarter-finals in 2007.
However Roma are currently undefeated in Serie A after five games and are jostling with champions Juventus for domestic supremacy.
Defeat for City, meanwhile, would leave Pellegrini's side in the Group E doldrums
Either way, Mancini said he expects a "spectacular game"
"It will be a spectacular game
City play a different kind of football compared to the other English sides: they keep the ball on the ground and move it around a lot, and they're able to vary attacking from the wings to attacking down the centre.
"Roma play football, as we used to say
City are not the United of several years ago
And this could go in Roma's favour."
Source : AFP