Mitchell,
Your question probably could have a complex answer… but…..in short getting an even roast is not a hard thing to do. Quality of the roast is ALWAYS exceptional, reliable and repeatable provided you set things up properly…… there are user-error situations that can cause an uneven roast…. such as roasting at low rpm (less than 6-10RPM), or without the drum being level, or with insufficient heat, but provided the roaster is set up with care, uneven roasts are not at all an issue.
See this article for a more complete answer:
https://blackbalsam.co/rkdrums/index.php/articles/40-
Thanks for the email,
Shane