The Blues’ midfielder claims that his compatriots were not aware of any controversial remarks from the referee during Sunday's game until after the final whistle
The 21-year-old was an unused substitute on Sunday, but it is his Spanish team-mate Mata who is among the players said to have taken offence to some of the language used by Clattenburg during the game.
The key exchange, however, occurred between Clattenburg and John Obi Mikel in the immediate aftermath of Chicharito's 75th minute winner, during which the Nigerian was booked for dissent.
According to Romeu, though, Chelsea's Spanish contingent were not aware of any comment at the time.
"Neither Juan nor Fernando told me they heard it because from what I have understood they didn't hear anything," Romeu told Spanish radio station Cope.
"It was someone else who heard it, but not directly at them. It was another player who heard it and that is what they told me.
|BET 365 LATEST
|20/1||Chelsea are 20/1 with bet365 to beat Man Utd 3-2 in the Capital One Cup
"I didn't hear anything as I left quickly to go home but after talking to Juan he told me there was some problem and he had to stay.
"I only know Chelsea made a complaint and I think there could really be a problem if what Chelsea players say happened really happened."
The incident is the latest in a string of controversies involving racism in football over the last 12 months, including the Football Association finding both Luis Suarez and John Terry guilty of using racially aggravating language during matches.
Subsequently, dissatisfaction with some of the game's leading anti-discrimination campaigns, most notably Kick It Out, has been voiced by a number of high-profile players.
Clattenburg will not be officiating a game during the weekend of November 3-4 as the FA continue their inquiry into Sunday's incident in response to the formal complaint lodged by Chelsea.
Romeu, though, is confident that the issue will be dealt with appropriately.
"We know in this country people are very vigilant about these issues," he added.
"If there was really a racist comment or something said against a Spanish player this will be serious."