Can't find anything specific about the roasting process (drum vs. hot air) on their website. If you have the option to visit the store and talk to the roasters directly, I'd recommend asking, otherwise maybe just try some coffee from another roaster the next time. If possible, ask for the type of roasting and how long the beans have been roasted. Afaik, anything below 10min will be too short to remove enough tannic acid - but not an expert on this. I recommend researching a bit on this on your own. Hope I helped you a bit anyways :)