The Group E clash, which ended in a frustrating 1-1 draw for the Barclays Premier League champions, attracted a crowd of just 37,509 at the Etihad Stadium.
That was City's lowest home attendance since they first entered the competition in 2011.
Scholes claims City's Champions League matchdays do not generate the same excitement as he experienced at United or other English clubs can create.
Scholes, who was working as a pundit for ITV, said: "I was lucky enough to play at Old Trafford and we always talked about the atmosphere on a Tuesday night, the special atmosphere you create, and the crowd is rocking when you go out for a warm-up.
"At quarter-past seven, there's empty seats everywhere
When you come here it just doesn't have a European night feel to it
You go to Liverpool, you go to Old Trafford, you go to Chelsea, they have a special feeling for it.
"I don't think they realise what a big game this is
They've got the team, they've definitely got the players, the quality is definitely there, but do the crowd realise how lucky they are to be in this competition? I don't think they do."
Scholes' comments come as development work is being undertaken to expand the stadium.
City have planning permission to increase capacity to around 62,000 and the first phase of construction, which will increase the number of seats to almost 54,000, is under way.
City's average attendance this season has been 45,612.
Another former United player, Rio Ferdinand, has questioned why this work is necessary in light of the latest crowd figure.
Ferdinand wrote on Twitter: "How many empty seats are there at the city vs Roma game by the way....big CL game & fans would rather Ramsays Kitchen or something at home.
"Expanding the stadium for what though?? For who though???"
The underwhelming result left City again facing an uphill struggle to qualify for the knockout stages.
Manager Manuel Pellegrini, however, had no complaints about the crowd.
The Chilean said: "Of course if you have a great atmosphere it is always better for the team but we cannot be concerned about the atmosphere the fans give because they always give very good atmosphere.
"I don't think that was an important thing why we didn't win the game."
Source : PA
Source: PA