Stability, not sustain. Taken verbatim from the Sadowsky website:
"Sadowsky Guitars has always taken pride in the quality and stability of our neck wood. We are now pleased to offer "roasted maple" necks for an unprecedented level of stability. Lumber for maple necks and fingerboards is placed in a special oven after normal kiln dying. The wood is roasted at temperatures ranging from 180º to 220º Celsius. The result of this treatment is wood that is significantly more resistant to absorbing or releasing moisture. With this increased stability, the "roasted maple" process enables us to offer figured maple neck blanks for the first time in our three decades of instrument making. We have always advocated that figured neck stock was too unstable to use. However, any piece of wood than has a stability problem will warp during the roasting process and be discarded. It would also be a recommended option for players who reside in areas of extreme humidity (low or high), or who travel a lot through variable climates, as well as players who desire a figured maple neck for aesthetic reasons."
The stability factor is nice, but I love the darker color and option to have a figured maple neck (not just fingerboard).