The 24-year-old British beauty is widely considered to be one of the sexiest women in the world but when she was growing up she admits she resembled the spectacle and brace wearing character Betty Suarez from the TV series.
Speaking in the new issue of America`s Harper`s Bazaar magazine, she said: "I was a bit of an Ugly Betty when I was 15."
Rosie revealed she would arrive at castings "in trainers, with braids, a ton of make-up, plucked eyebrows and I had braces".
The catwalk star - who is dating Jason Statham - recently made the transition from modelling to acting with a main role in `Transformers: Dark of the Moon` and she admits she initially found it difficult to adjust to the movie business.
She said: "It`s interesting coming from modelling, where women rule the industry, into one where there are so few great female parts and the competition is so much higher."
Rosie is very proud of her first screen role, but she admits she still takes immense satisfaction from being a Victoria`s Secret Angel, because being a face for the underwear giant is one of the biggest jobs in modelling.
She said: "It`s still such a huge thing for a model. People kind of laugh about it and think it`s irrelevant, but I don`t know a girl in the world who would put those wings on and not feel, just for a split second, very special."