What is Rate of Rise (RoR) in coffee roasting?

Rate of Rise (RoR) is the speed at which bean temperature increases during roasting, expressed in degrees per minute. It is one of the most closely monitored parameters in precision roasting, allowing the operator to actively steer the heat profile and anticipate transitions between the key phases of the process.

Rate of Rise is fundamentally a derivative: it measures not the absolute bean temperature but the speed at which that temperature changes at any given moment. If the bean probe reads 160°C at t=5 min and 170°C at t=6 min, the RoR at that instant is 10°C/min. It is this dynamic — not the temperature value itself — that guides decisions for professional roasters.

A well-managed RoR profile typically describes a declining curve: high early in the roast (sometimes 15–20°C/min just after charge), then progressively reduced as the batch advances. This controlled deceleration is intentional — it reflects the growing energy contribution of exothermic reactions (Maillard, caramelization) that partially self-sustain the process. A RoR that remains flat or spikes too late can create baked profiles or uneven development.

RoR is closely tied to the distinct phases of roasting. During yellowing (the drying phase), RoR is moderate and declining. As first crack approaches, it tends to drop more steeply — a sharp RoR crash just before first crack often signals insufficient energy in the system. After first crack, RoR management determines the speed of development and therefore the final flavor profile: a higher RoR during development produces brighter, more acidic coffees; a lower, extended RoR favors body and chocolatey notes.

In Cropster and Artisan roasting software, RoR is displayed in real time as a secondary curve overlaid on the temperature graph. Experienced roasters read this secondary curve as carefully as the temperature itself. Spikes or troughs in the RoR signal thermal imbalances — for instance a gas adjustment that was too abrupt, an inappropriate charge weight, or a variation in bean heat capacity due to origin or processing.

There is no universally 'correct' RoR value: everything depends on the coffee (density, moisture, processing), the equipment (drum, air roaster, capacity), and the target flavor profile. What matters is consistency and reproducibility: the same coffee, roasted with the same RoR profile, should produce a similar result batch after batch. This is what distinguishes reproducible artisan roasting from intuition-based approximation.