The 30-year-old becomes the latest Italian marksman to return to his former side, while they have also completed a year-long deal for Uruguayan goalkeeper Mauro Goicoechea
The Giallorossi have also confirmed that goalkeeper Mauro Goicoechea arrives from Uruguayan outfit Danubio for the coming season, with a view to a permanent deal.
A statement on Roma's official website reads: "Roma announce that Marco Borriello has signed with Genoa. The contract for the loan transfer expires June 30, 2013, for a fee of €250,000.
"Daniel Goicoechea has signed from Danubio. The contract for the temporary acquisition of the player expires June 30, 2013, for a fee of €100,000.
"The agreement also includes the option to purchase him outright, from the season 2013-2014, for €700,000."
Borriello, an Italy international, was deemed surplus to requirements by both Luis Enrique and Zdenek Zeman at Roma, and had spent the second half of last season at Juventus.
However, he failed to earn a permanent transfer to the Old Lady and will now resume his career at Genoa, whom he scored an impressive 19 goals for in the 2007-2008 campaign.
Meanwhile, Goicoechea, 24, moves to the Olimpico after six years and 60 appearances at Danubio.