A source told The Sun: 'They'd obviously been watching Roberto come and go, then swooped in.
'It's thought they are the same guys who were disturbed mid-burglary on a previous occasion.
'He was obviously shaken up as he has a young family, so the club had him in a hotel before giving him security at the house.'
Forensic tests have been taken at the property and the gang are believed to have been wearing hoods, with one in a blue Puffa coat.
Detective Inspector Steve Christian, from Liverpool CID, said: 'I'd like to appeal to the consciences of the offenders and ask them to put themselves in the victim's position and think how they would feel if this happened to them.
'While the occupiers were not in at the time, it has clearly been very upsetting to find their home has been targeted in this way.
'I would ask the offenders to do the right thing and return the stolen items to the owner in any way possible.
'I would also like to appeal to anyone who might have been offered the items for sale since the burglary to contact police, and anyone who was in the Carnatic Road area on that night to contact us if they remember anything suspicious.'
The incident happened on December 22 and just days after the Liverpool forward was charged with drink-driving after being pulled over by police.