The 32 year old singer proposed to Rosanna on December 23, which was also her birthday, reported Contactmusic.
"It is with great pleasure we are pleased to announce the engagement of Antony Costa and his beautiful girlfriend Rosanna. Antony surprised Rosanna on her birthday today with a visit to Paris where he asked for her hand in marriage and she happily said yes," a statement on boy band Blue's official Facebook page read.
"Everyone in Blue and the entire management team wish both Rosanna and Antony the very best for the future and we are all looking forward to the wedding," the page added.
"We're Engaged!," she wrote.
Antony also thanked fans for their wishes as congratulatory messages came in.
"Thankyou for your lovely messages myself and Rosanna Jasmin are so happy to announce our engagement!!! Bring on 2014," he tweeted.