Elevation and Growing conditions can change the way you roast.
Higher altitudes and harsh conditions can slow the growing process of the plants causing different sugars to develop over time, impacting flavor in great ways. A slower growing process also can change the density of the coffee beans. The more density the beans have, the higher the heat resistance will be.
Harsh conditions could mean many things such as
Although there are many diagrams to explain coffee flavor based on altitude, they aren't always as accurate as we'd like to think. Coffee grown at the same altitude, but in different parts of the world can show vast differences in flavor. For example, Some of the coffee flavor charts say that coffee grown at 5,000 ft+ will show signs of fruity, floral and spicy notes. Yet some coffee from Nepal shows rich caramel and smooth creamy notes.
Another tricky thing about identifying higher altitude coffees is knowing the different words used on the packaging. Much like words used for the processes used when drying coffee beans, the words used to explain the elevation coffee is grown at changes region to region. Hard bean, Strictly hard bean, Mile High and Altura are all different phrases and words I have come across for coffee elevation. Shade grown plants have also been referred to as "bird friendly' as well, due to not needing as many pesticides, thanks to the birds in that region.
High grown beans in Costa Rica are far different from high grown beans in Ethiopia, based on Costa Rica's highest coffees are grown around 4,500 ft above sea level, where in Ethiopia they are grown around 6,000 ft. That goes for anywhere really, coming back to the words used, they all change with origin. Hawaiian coffee beans are usual found at a lower altitude, like most other island grown coffees, But the difference in flavor may surprise you. Most Hawaiian coffees are shade grown, which slows maturation of the plants, letting more sugar develop. also the drainage in their soil helps keep water levels lower and keeps cherry size smaller. This applies to mountain grown coffees as well. Another great thing about different elevations; only certain plants can grow at higher elevations, lowering the risk of disease spreading to the coffee plants.
WHY THIS IMPACTS ROAST
Lower grown coffees have different solid bean structures than higher grown coffees. As the elevation increases, so does the bean structure. this is caused by the different natural gasses that occur inside the beans as they grow. Lower grown coffees may have a quicker reaction to heat, so its advised that you use lower/softer roasting methods depending on bean origin. Higher density beans may take a high initial heat when roasting to help excite the beans to crack.
There are a lot of things that can change the flavor profile and density of Coffee beans, in the end, my biggest recommendation is to try and measure the density before you roast a new coffee. Get to know that coffee next to the others you have worked with on other occasions. This will help you recognize the differences over time, and make you a better roaster.