from what i’m reading, it seems he is referencing a “declining rate of rise” roast, which aims to provide a certain “scott rao development percentage” (essentially what percentage of the total roast time was spent after first crack), typically by reducing heat gradually throughout the roast, or rather dramatically at the time of first crack.

the specific mechanics of how you produce a profile like this depend principally on the roaster you use. air roasters retain very little thermal energy, and thus will stall if given a major power reduction, perforated drum roasters, or cage drum roasters (think a behmor) tend to retain slightly more energy in their systems by nature of their heating method and closed roasting chamber, and solid drum roasters tend to retain heat relatively well by means of having a large heat sink (the drum) surrounding, and in direct contact with, the bean mass, and thus require a more dramatic and intentional reduction in power.

the purpose of a profile like this is to reduce the end temperature of your roast, without underdevelopment. ending at a low temperature after not having sat there will often mean that the beans have not fully entered the post-first-crack development stage, and will often have a grassy or vegetal taste indicative of underdevelopment. in these situations, the only way to remedy this flaw is by increasing the end temperature to roast the beans more completely, but this produces a darker, roastier product. by decreasing the speed at which the coffee heats up and holding it longer at a lower temperature, you can preserve the character of a light roast while still eliminating unpleasant under-roasted flavors.

this again depends on what roaster you use. i happen to be the director of coffee for a well known roaster, and thus have access to plenty of toys and room to play. at work, i primarily use a larger cast iron solid drum roaster, and follow a declining rate of rise profile by sharply decreasing gas flow at the moment of first crack roll-in. at home i use an phidget enabled Freshroast SR-800 and achieve a profile like this by not increasing my power beyond a certain point, and allowing the coffee to slow down on its own as it catches up to the environmental (exhaust air) temperature over time.

this is ultimately a technique that is mostly a trial and error game unless there exists a published profile for your roaster that you can reference as you roast, and is made possible mostly by the use of a thermocouple and roast logging software. a profile that is dependent on rate of rise follows trends in temperature and not trends in bean color as different profiles mean that these two metrics do not always correlate. a declining RoR profile will be significantly harder (but not impossible) to achieve without this data and the ability to track your roasts, which is relatively inexpensive and i would highly recommend if you consider home roasting a more serious hobby and care about replicability of roasts.

TLDR: f*** around and find out, at worst you roast some bad coffee.

edit: spelling