Borriello has fallen out of favour at Roma under the management of Luis Enrique and had been linked with a January move.
Juve have agreed a deal worth 500,000 euros (£417,000) up front, with a further 8million (around £6.7million) due to sign the 29-year-old at the end of the loan.
Borriello told Juve's official website: "I am truly honoured to be here. For me it is very exciting and is a great sign of esteem from one of the biggest clubs in the world.
"I hope to showcase my talent and do my best here."