The 23-year-old stood out in Aironi's Heineken Cup matches last term and has been included in the Italy squad for forthcoming matches with Argentina, Canada and the United States.
Saracens director of rugby Mark McCall is confident Romano will add depth to the team's front-row stocks.
McCall said: "Lorenzo made an impact for Airioni last season and was recently included in the Italy squad.
"He is a young prop with immense potential, and we are looking forward to providing an environment where he can develop into one of the leading prop forwards in Europe."
And Romano is confident his career will come on leaps and bounds with the move to Vicarage Road.
"Saracens is a dynamic and ambitious club, and I am very pleased to have this outstanding opportunity," Romano said.
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