Coffee first came around about 1000 years ago, but it wasn’t until the 1400s that coffee roasting technology really started to take off, beginning in the middle east. The first methods weren’t really that fancy and really just consisted over a large flat spoon that got placed into a fire, with a smaller stirring spoon to help evenly roast everything.
As time went on, it started to become a flat perforated pan with a long handle that was placed over a large container of coals. Still not too fancy, but it got the job done. A couple hundred years later a large cylinder with a crank was developed to allow for roasting higher quantities.
Although there were coffeehouses starting to sprout up in Europe throughout the Renaissance period, coffee roasting largely happened in homes in small batches until the late 19th century. General stores typically just carried green coffee beans, and you could even mail-order green coffee beans as the only real way to access coffee. Until that point in time, most coffee roasting related inventions were in regards to home roasting, and being able to attach them to certain stoves, or to keep certain vapors from ruining the flavors. Most people simply roasted their coffees either by cooking them in a single stack on a pan-like object held over heat, or had a gadget that helped stir beans to be able to hold and roast more than one layer of beans in one spot.
During the mid 1800s more people started figuring out ways to roast massive quantities of coffee all at once. Then, according to the book Uncommon Grounds: The History of Coffee and How It Transformed The World, in 1864 the selling of one pound bags of roasted coffee really took off due to economies of scale and these large commercial facilities really being able to out-compete with the home roasters. Later that century, hot gas roasting was discovered, and the whole process became much quicker. However, it wouldn’t be until the 1900s that sales of pre-roasted coffee finally surpassed the quantities of those created by home roasting.
Virtually all roasting to this day has been through some variation or another of using hot air to either directly or indirectly roast beans, done in more and more complex and creative ways.