I am curious what this gas part at the bottom is? Would this correlate somewhat to our input temperature?
Yes. It’s the percentage of gas capability of the roaster being used through the roast. That will usually be applied manually turning up/down as you go.
The first part is different as beans are added to the roaster it brings the temperature down so a swift application of max gas is needed to get the temperature back up and enough energy in the system to roast the beans.
The gas is turned down gradually to keep the RoR line falling steadily in an approximate straight line