I think there was a thread about this a while back in which the OP asked what the difference is, and about a dozen people (me included) told him that they are the same. Maybe i’m remembering it wrong, but I know that I’ve never known the difference.
I just found a section on it in Brewing Classic Styles, and I thought I’d share what I found, and what I don’t quite get yet.
As I read it, Palmer essentially claims that kilned grains retain their diastatic power and only undergo Mailard reactions during the kilning process (no carmelization). It seems that the kilning process takes place without oxygen, and mainly dries them out. This includes things like victory and munich that can be steeped for character, but are not already converted.
Again, as I read it, Palmer says that roasted grains are roasted in the presence of oxygen and higher moisture, so they convert during the roasting process, and there is carmelization of the sugars that takes place.
There are some grains that are both kilned and roasted. They start out as green malt, but whereas crystal malt is roasted while it’s still moist, these are kilned to dry them before they are roasted. Chocolate and black malts are in this category.
So kilning malt is done at low temperature to dry and make they slightly toasty and biscuity, but roasting is done at higher temperatures on either dry or moist malt that has already been converted, to produce caramelization, dark color, and dark, chocolate, and coffee flavors.
Anybody have something to help clarify this?