Did you contact whomever replaced the main board? Was the power to the furnace turned off when the board was replaced? Why was the board replaced? Did the furnace every work properly with the new board?
Jumper the roll-out switche(s) TEMPORARILY (observing the flame as the furnace starts). If you still have the issues then I think the board is bad. If you turn off power to the furnace for 15 minutes you should reset the board and the fan should stop. If the fan does not stop, another bad board indication. Double check that the thermostat isn't set to FAN-ON.