No stain. There's at least one lumber supply company that's using a fairly exotic heating process to expose raw wood to considerably higher temperatures than a normal drying kiln, without burning it up.
The effect on the lumber goes considerably beyond simple moisture removal. Apparently, cooking the resins in the wood changes the physical properties such that it's a little harder, and more stable. It also darkens the colour in a way that mimics a good stain job.
I have a luthier friend (mainly acoustic guitars, not basses), and he's been experimenting with some roasted maple he picked up. It's way different than a stain job, in that the colour goes all the way through the wood.
Tonally, it seems to have a higher resonant frequency than an average piece of maple. It feels very resonant, and it machines like it's three or four clicks harder than untreated maple.
The jury is still out on stability until he's had more experience with it, but the piece he has looks promising- no lateral runout, etc. Of course, that will have a lot to do with the pieces they choose to put through the oven, as much as the heat treatment process.
I don't think necks are roasted, but entire logs go into the oven.
Bwahahaha
