Nuts punish guesswork
Roast coffee and the beans tell you where you are. First crack, second crack — you can work half by ear.
Nuts tell you nothing. There is no crack, no reliable sound, no moment of announcement. What there is instead is oil: peanuts, pecans, almonds and cashews are somewhere between a quarter and three-quarters fat, and fat carries heat. That combination — no audible cue, high oil — is why nuts go from pale to acrid in under a minute, and why so many people scorch a tray and never quite work out what they did differently.
Three things that make nuts their own problem
They keep roasting after you stop
A tray of hot nuts is a lot of stored energy in a lot of fat. Pull them at the colour you want and they will carry on past it while they sit. This is the single most common reason a roast that looked right tastes over-done — the roast did not end when you thought it did.
They are physically large
A pecan half or a peanut in its shell is many times the size of a coffee bean. Inside a drum, the vanes — the ribs that lift and tumble — are sized to the product. Vanes cut for coffee do not leave a nut enough clearance to toss, and product that cannot toss does not roast evenly. We cut the vanes about an inch shorter for nuts and cacao.
Shell or no shell changes everything
A peanut in the shell and a shelled peanut are different roasts. The shell is a barrier and a buffer; it slows the heat reaching the kernel and it changes how the batch tumbles. Times from one do not transfer to the other.