United were linked with a move for De Rossi during the summer transfer window as Moyes looked to bolster his midfield options.
United were reported to have had a bid for De Rossi turned down by Roma and Capello claims Moyes did seek his expert opinion on his fellow Italian having worked with him during his time in charge with the Giallorossi.
The former England manager also revealed that if he was De Rossi he would have pushed for a move to Old Trafford.
"A few months ago David Moyes asked me for my opinion about De Rossi and my opinion could only be positive," Capello told Fox Sports.
"If I were De Rossi, I would have gone to Manchester United.
"I would have wanted to go to a club where the ambition is very high."