Roberts has been out for seven weeks but has returned to training, although Wednesday's visit of Millwall will come too soon.
Gary Gardner remains out with the calf injury which has sidelined him for two months.
Norwich loanee Przemyslaw Placheta (shin) has not featured since August while Nico Gordon is close to a return having been out all season with an unspecified problem.
Benik Afobe is a doubt for Millwall after suffering a knee injury in Saturday's defeat at Huddersfield.
The striker came off late on in the 1-0 loss and did not train on Monday. He will be assessed ahead of the game at St Andrew's.
Murray Wallace, Ryan Leonard and Shaun Hutchinson are all out for boss Gary Rowett, who managed Blues between 2014 and 2016.
Isaac Olaofe missed the game at Huddersfield with illness but has returned to training.