How to Roast Coffee Beans

One of the best ways to enjoy coffee is undoubtedly by roasting the beans yourself. When you take the time and put the effort in to roasting coffee in the comfort of your own home, you will be able to guarantee that every single cup you make will be the freshest and tastiest (once you’ve mastered the skills) you have ever tasted.

Therefore, rather than always heading out to your favourite coffee shop or purchasing pre-roasted beans or coffee grounds, why not take the dive and try roasting your beans yourself. We will warn you though, that once you start, you are likely to become addicted to it pretty quickly and won’t ever want to get pre-roasted beans again.

Before we go any further into explaining how long it takes to roast coffee beans, how you can use your oven and other appliances to do the job so you don’t need to invest in a purpose-made coffee bean roaster, we are going to discuss why you need to roast coffee beans in the first place.

Do Coffee Beans Need to Be Roasted?

To help you understand why we need to roast coffee beans before using them for beverages, you need to understand its origins. Coffee beans begin life as small red fruits that have a number of different stages, they need to go through to get them to the point where they can fill our cups with that beautiful liquid.

First the coffee is picked from its plant and processed, during which time the parchment skin on the inside, the pulp and the outer skin are all removed. After that stage, the inner seed, which is what we know and love as a coffee bean, is then dried.

It’s during the drying stage that it becomes a green coffee bean that is ready to be shipped out all over the world to be roasted. Similar to dry pinto beans, coffee beans can be in storage for extended periods and still retain freshness once they are roasted.

What would happen if you tried to drink coffee made with unroasted beans? You’d have a very unpleasant drink indeed that tasted incredibly acidic and bitter.

It’s during the roasting process that the coffee bean develops its unique and delicious scents and flavours. Roasting coffee beans forces all the moisture, retained inside it, out making it dry out and expand. All the while, some of the bean’s natural sugars are transformed into CO2 while many more are caramelized and produce those flavour notes that help form the complete taste we have come to expect of coffee.

Once roasting is completed, the once green coffee bean will have been turned into a beautifully brown bean that is around 50 to 100% bigger than it started and weighs 18% lighter.

How Long Does it Take to Roast Coffee Beans?

Now that we have discussed what is involved in the roasting process and why it is a necessary part of preparing coffee beans for brewing delicious pots and cups of coffee, you are probably wondering how long the process of roasting actually takes.

It depends on the amount of coffee beans you are going to roast. If you are only planning on roasting a small batch of beans, it could take you between 10 to 13 minutes to roast them to perfection, whereas if you intend on roasting a much larger batch, it might take anything from 16 to 18 minutes to roast them.

Can I Roast Coffee Beans In the Oven?

Now we know why roasting coffee beans is so important and how long it takes, you will probably be turning your attention now to equipping yourself with the right tools and appliances to roast beans. As not everyone wants to rush into buying a brand-new coffee beans roaster, whether you are planning on doing so but at a later time or are not even sure you want to own one.

Therefore, you may be interested in alternatives. Alternatives that you already own and that are in your home. You’ve probably asked yourself before, simply based on the vocabulary used, whether you can use your oven to roast coffee beans like you use it to roast a chicken.

Well, the process is probably a lot closer to making popcorn, but yes you can use an oven to roast coffee beans.

Before you pop some coffee beans in a baking tray and watch them burn, there are some things you need to make sure you have close to hand, including:

  • A baking tray – one with very small perforations, similar to the kind you would use to cook a pizza with
  • Stopwatch or timer
  • Wooden spatula
  • Metal colander you can use when it’s time to cool the beans
  • Coffee beans
  • Flashlight (if your oven doesn’t have a working light)

Your oven needs to be able to ideally reach temperatures of 470 to 500-degreees Fahrenheit and there should be a viewing window you can use to keep an eye on the roasting process. This Is crucial.

Preparing to Roast

There are a number of things you need to do once you have all the things listed above. First of all, you need to spread out the beans onto the baking tray or pan you plan on using, being sure that they don’t touch, and they are spaced out enough. Avoid stacking them on top of each other, as this will cause problems once they start expanding.

The tray is not the only thing you need to prepare. You need to ready yourself for the amount of smoke that is produced while you are roasting coffee beans. The larger number of beans you roast, the darker the roast will be, and the more smoke will be produced. Open windows and make sure your home is properly ventilated, to avoid setting off the smoke alarms.

You then need to plan out what you are going to do when you take the beans from the oven. Although there will be the chaff, the thin layer of tissue-like material that will need to be removed before grinding them, the most important thing you will want to do immediately after roasting is to cool the beans down.

The aim is to reduce their temperature to room temperature as quickly as possible, so they don’t continue to cook and spoil. Allow yourself space to get from the kitchen through to your back garden or just outside your property and keep a metallic colander there.

Roasting the Beans

When you are ready and the oven has preheated, place the tray with the beans on in there, watch and listen. The beans will take between 10 to 17 minutes to roast. If you notice any unevenness during the process, open and stir them up a little with a spatula, being careful to not leave them out of the oven for too long.

Cooling Them Down

Once they have finished and resemble roasted beans you need to quickly take them to the cooling area you set up outside. Place them carefully into the colander and then use that to shake them down to room temperature, this will also help remove the chaff.

You then have roasted beans that, once they have stood for 24 to 48 hours to degas, can be used to make a delicious cup of coffee. You will then be able to enjoy the enormous sense of worth and achievement. Pat yourself on the back.


We hope this guide to roasting coffee beans has been as interesting and enlightening for you reading it as it was for us researching and writing it. There are many other ways you can roast beans at home, that we will likely tackle in different posts. We wanted to discuss roasting using an oven, because it is the one thing that everyone will have in their house ready to use.

Although it is perhaps not as simple as you initially thought it may be, we have hopefully shown that it is also not widely impossible. Preparation is the key.

Happy roasting, grinding and brewing, but just don’t blame us if you start a fire!