The 32-year-old has been signed as back-up to first-choice ‘keeper Mile Svilar for Daniele De Rossi’s team.
He joins Roma after being released by Eredivisie outfit AZ Alkmaar at the end of last season.
Ryan has 93 caps for Australia and played for the Socceroos at the last three World Cups.
Roma, who finished sixth last season in Serie A, begin their 2024/25 campaign at Cagliari on August 18.
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