Low setting doesn't always come into play when roasting. You could use Low if you only have 50 grams to roast for example. But that probably won't be the case often. Again ... to be clear ... do not use low setting if it is not moving the coffee adequately, as shown in our video! If the coffee isn't moving it will burn on the bottom later very, very quickly. Low fan setting is very useful later in the roast though, for people who want a bit more development at the end, or find their roast has stalled and isn't progressing. It might seems counterintuitive, but Low fan speed will heat the roast batch to higher temperatures, because less heat is being pushed past the coffee and out of the roaster.