The Egypt international spent the second half of last season on loan at Fiorentina, where he made a massive impact, netting nine times in 26 appearances.
The Viola were under the impression that they had agreed a deal with Chelsea that would see Salah remain at the Artemio Franchi for the 2015-16 with the option to buy next year.
However, the attacker's agent claimed that his client was free to return to Stamford Bridge and then decide where to go next, having already been deemed surplus to requirements by Blues boss Jose Mourinho.
As a result, even though Fiorentina threatened legal action, Salah has now moved to the Stadio Olimpico, with capital club paying an initial €5 million for the right to take the 23-year-old on loan.
“I think Roma are one of the biggest clubs in the world and I'm happy to be in this team," he told the Giallorossi's in-house TV channel.
"I think everybody here has ambition and everybody wants to win the title.
"Everybody will give their best to make the fans happy.”
