Charlton overcame Leicester City in extra time last week to take their place in round five.
The Robins have also beaten Soham Town Rangers, Yeovil and Cambridge United having entered the competition at the first round stage.
We scored a late winner in round three at Stevenage before a fine win in the fourth round at Cardiff City.
This match will be played to a finish on the night, so will go to extra time and then penalties if required.
The winners will travel to the winners of the fifth round tie between Swansea and Manchester United in the quarter-final.