Doni sealed his switch to Merseyside earlier this month after six successful seasons in the Italian capital.
The shot-stopper, who has signed a two-year deal with Kenny Dalglish's side, admits joining the Reds was an offer he could not turn down despite being happy in Serie A.
The 31-year-old will provide cover and competition for Pepe Reina and the Brazilian custodian is delighted to join such a famous club.
"It is an honour to be at a club like Liverpool after leaving Roma," Doni told skysports.com.
"I was happy at Roma, but Liverpool is one of those clubs that when the opportunity to go there comes along you have to take it with both hands.
"I would like to thank everyone at Roma and the fans for what they did for me during my time there and I am excited about my new challenge at Liverpool.
"I would also like to thank my agent Ricardo Sarti for making it happen.
"I am looking forward to playing for the Liverpool fans and it will help I will have my fellow Brazilians Lucas and Fabio Aurelio there to help me settle in and I promise to do my best for the club."