Ali Saeed's daughter of Authorized had a dream run round under Andrea Atzeni, tracking the leaders before taking up the running on the final bend.
The field were stacked up in behind but Ambivalent stuck her neck at gamely and it was only top Japanese mare Gentildonna and multiple Group 1 hero Cirrus Des Aigles who got past her.
Ambivalent, already a Group 1 winner in Ireland last year, secured £300,000 in prizemoney.
Roger said: "I am incredibly proud of Ambivalent. She has put up a career best performance and was beaten by two exceptionally good horses.
"Andrea has given her a lovely ride and Ambivalent has given her all. Paul Dell, who rides her everyday, has done a great job at getting her settled but it is a team effort and I am thrilled for everyone at home."
Ambivalent in Dubai enjoying a pick of grass with Paul Dell