Source: Official AS Roma
Official statement of the club confirming the agreement with the player.
As stated a few days ago (read here), Seydou Keita was really close to the club and he was expected in Rome today to sign the contract.
This morning he arrived and signed it, so the deal is closed. The contract lasts one year, expiring on 30 June 2015.
Official statement here!
Official Tweets here!