The Preachers

The parallel-universe that spawned the Cybermen in 'Age of Steel' is also home to members of a secret organisation dedicated to fighting and defeating the Cyberman menace which still exists in their universe.

The resistance is led by Rose's father, Pete Tyler, still alive in this universe, and he was joined by the Mickey Smith from our universe.

The resistance were able to cross into our universe when Torchwood began to draw power from the Void Ship (Army of Ghosts]]) and hoped to use this as an advantage in defeating the Cybermen, still rampant in their home universe. They returned following the defeat of the Daleks and Cybermen (Doomsday), taking Rose with them, trapped in the alternate existance when she fell through the void created by The Doctor.

It's to be assumed that Rose, supposedly separated forever from The Doctor, now leads a major role within the resistance.