New Robins boss Gary Johnson said: "It's a big ask for a player to go straight into the side without a training session.
"But Osei's an intelligent footballer capable of handling a situation."
Sankofa has made just one appearance for the Addicks, against Manchester United in 2002/2003.
"But Osei's an intelligent footballer capable of handling a situation."
Sankofa has made just one appearance for the Addicks, against Manchester United in 2002/2003.