The 33-year-old former Argentina international was officially presented on Saturday after his move from Marseille where he spent the previous two seasons.
“It’s a great honour to wear this shirt,” Heinze told reporters. “It’s easy to say yes to a club like Roma.”
Heinze played for Argentina at the last two World Cups, although his omission from the squad for this year’s Copa America suggested his international career may have ended.
Roma, who finished sixth last season to qualify for the Europa League, last month appointed former Barcelona and Spain player Luis Enrique as coach.
On Friday, Barcelona announced they had agreed to sell 20-year-old Bojan Krkic to Roma for 12 million euros in an unusual deal that includes a commitment to buy the Spain under-21 forward back in two years.
Roma have also signed 19-year-old attacking midfielder Erik Lamela, considered one of Argentina’s brightest prospects, from River Plate.