With the Roomba upside down, remove the 10 screws that hold the front bumper retainer plate and lift it off and away. Then lift the front bumper away from the robot. Be careful not to damage the ribbon cable that plugs into the Circuit Board.
With the Roomba sitting flat,remove all the screws on the top panel except the two screws holding the Roomba handle. Begin lifting top away from the bottom base of the robot. Lift evenly on all sides to free the top off of the base.