The two star together in new romantic comedy Ticket to Paradise, the first time they have appeared in a film together since Ocean's 12 in 2004.
Clooney joked: "Depends on the friend."
He then talked about kissing Roberts with his family on set: "My wife and kids came to the set the day we were doing it. You know, take the kids away. Anything but watching papa kiss [Julia]."
Roberts added: "It’s kinda goofy, kissing anybody that’s not your person is strange."
Clooney also spoke about agreeing to do the film, his first romantic role in a long time: "We both said at the same time 'if you do it, I’ll do it'. I don’t think we could’ve done it with anybody else, that’s kinda how it felt."
Roberts also said: "We were sent it [the script] at the same moment, and there was a strange synchronicity to both of us being around at the same time to read it."
Ticket to Paradise follows two divorced parents played by Clooney and Roberts who work together to try and sabotage their daughter's wedding to a man she has only just met.
The film also stars Kaitlyn Dever and Billie Lourd who is the daughter of Star Wars legend Carrie Fisher.
Ticket to Paradise was originally supposed to be released in the UK on 16 September but that was delayed following the death of the Queen a week earlier.
The rom-com was eventually released on 20 September.
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