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Honestly it's not too tricky. My first few attempts were using one of these https://www.triplebarcoffee.com/equipment/roasting/nuvo-eco-coffee-roaster-review/
and a camping stove.
Definitely under-roasted a few times before I got a decent enough idea of what they should look like (a few very weak, and very grassy tasting coffees were had in the first attempts)
If you listen for when they start cracking, and keep a close eye on them afterwards so they don't full on burn up, you can't go too far wrong.
Of course, that's just for roasting things to a level where they are drinkable. After that, it's a bit more practice to get more consistent roasts, then tweaking things to taste.
I’ve always fancied roasting my own coffee.
I wonder how many kg I’d ruin before I got it right