There will be no swap deal involving Fernando Torres and Roma's Mattia Destro, according to the Italian player's agent.
Nottingham Forest boss Stuart Pearce is confident Henri Lansbury will sign a new contract with the club.
The 21-year-old Cameroonian has been training with Rovers for the past month and has signed a two-year deal after impressing in pre-season friendlies against Wrexham and Portimonense.
Songo'o, who is the younger brother of former Sheffield Wednesday loanee Franck, started his career in Spain before moving to MLS side Sporting Kansas City, where he was released from this summer.
Rovers boss Gary Bowyer has made strengthening his back line a major priority and adds Songo'o to a defensive pool including fellow new signings Tommy Spurr, Matt Kilgallon and Todd Kane.