The 33-year-old former England international striker has signed a performance related short-term contract and goes straight into the squad for Saturday's game against Arsenal.
"Robbie has signed his contract," confirmed Rovers boss Paul Ince this Friday morning. "It has been a ongoing situation for the last two or three months now.
"But I'm pleased that he has signed , he's a proven goalscorer, it was not long ago that he was banging in goals at Anfield, so it shows that he can still do it at this level.
"It is a three-month contract and if he does well and does the business then there is no reason why we can't extend that."
