Preface: This is based on some of the open conclusions I have been slowly understanding. There are things I cannot physically have you taste nor know of how to perfectly apply it to your roaster. This is just a topic that will have to be mulled over, trial-ed (on your roaster) and generally a topic for thought an openness discussion. Saying words like "conjecture" would be a mute point so I hope we can have some clarity that we are speaking from our own references. So without further adieu...
I feel like there are actually three main areas for flavor development during the roast:
1) the charge, speed and length of green (creates the creamy coffee aroma in roasted bean, also where I add more or less heat based on Millard, too fast can cause tipping)
2) the Millard, speed and length (too short = pea/vague acid with no flavor, too long and hot = meat, long and not too hot = chocolate)
3) "Developement" (for clarity please refer this the phase beginning with a capital "D") too slow and coffee dies, too fast and coffee burns)
The umbrella topic: I would like to discuss how this all effects the "landing" of the roast. More specifically, the entry into Development. My ques for understanding a good roast is the development of flavors coming from my exhaust vent aka trier (I understand this is not a healthy option so I take quick sniffs). A great profile during the end of Millard or for some beans the end of Development I smell a fruit aroma, fruits are my goal. I used to chew on freshly roasted (directly after cooldown) and 10minutes rested beans and I could taste if there were fruit notes or others and generally how good or bad the roast was. When my roasts were landing (during the chaff release I call expanse, at the end of Millard beginning of 1C, I can smell either green notes (pea, cucumber etc) or fruit and generally try adding more heat before this on the next trial. If no smells I would readjust the total profile usually by adding more heat along the z-axis, since most of my profiling come from a low to high heat approach. (I am working from a roaster, Ikawa At Home, that only does preset profiles based on input heat) I use 1C sounds (loud or soft, lots of cracks or a couple and sometimes none. As an indicator for applying heat.
Recently I have taken to roasting (or reroasting some failed batches that didn't make it up to sniff (after resting in ziplock containers). I have noticed that if I stay along the course for a pea flavor with lots of heat and developing with a sharp roasted note this tastes exactly like most Starbucks roasts. This landing into and then developing that initial pea flavor turned into Starbucks, but usually I would have adjusted to get fruit on the nose (by enough heat from green and Millard) before Development, which to me and my profiling Development is just the area to make the bean more brittle and a good Dev would keep the fruit or (in the case of Sumatrans) create fruit (so I would be technically landing my roast for Sumatrans at the end of Development).
How do you, where do you "land" your roasts? Do you have indicators (what are they)? Do you agree/disagree with what I said?