After tearing apart a popcorn popper and in general, 'making it work the way I want' with an ESP32, I was able to add my other 'wants' such as some buttons and lights and put together a schematic in Eagle.

A few hours later and I had a PCB.

Now I just have to wait for it to arrive in a few weeks. In the meantime, I've got plenty to do: both the 3D printed enclosure to clean everything up needs to get designed and I need to write the actual code for the roasting process. This last part is dead-simple in practice, but since I'm making myself use ESPHome to control the ESP32 I think it will be a little more involved (I've never used ESPHome for anything other than making simple sensors, etc. in Home Assistant). It LOOKS like I can use a 'Generic Custom Component' to essentially just write some code like it's a normal Arduino project, but we'll see if this is actually the case.