Well...
I just finished an intensive 3 day hands on course of coffee roasting. I skipped the barrista training. But it was 3 days of roasting and cupping(tasting) of various coffees from Guatemala, Nicaragua, Ethiopia, Brazil, Columbia, Peru, India, and Indonesia. Coffee roasting is a massive attention to detail. Seconds and processes matter. There's a ton of knobs and dials on a coffee roaster and I was using them all.
5 degrees and 11 seconds make a huge difference in how your coffee tastes.