Bones and walnut or hazelnut shells have been found on excavated sites, but there is no means of knowing whether they are the remains of cooked meals, the debris of fires lit for heat, or even the remnants of incincerated raw waste matter...[researchers] are inclined to think the meat was roasted, from the evidence of Mousterain sites in Spain and the Dordogne..." ---History of Food, Maguelonne Toussaint-Samat [Barnes & Noble: New York] 1992 (p.90) "Food has long been baked in coals or under heated rocks, steamed inside animal stomachs and leaves, boiled in rockpots by heated stones, and so forth.Although a simple knowledge of edible plant resources could be transmitted easily enough in Pleistocene times, it seems unlikely that special methods of food preparation were devised before the Neolithic cultural level.
Taken back a few millennia and relocated in Europe this would translate into a piece of mammoth, venison or something of the sort falling in the campfire and having to be left there until the flames died down.
Berries, nuts, fungus, and water sources were especially complicated and concernful.
Myths and legends perpetuated the warnings against consuming known poisonous foods.
Improved health must certainly have been one result of the discovery of cooking, and it has even been argued, by the late Carleton Coon, that cooking was the decisive factor in leading man from a primarily animal existence into one that was more fully human'.
Whatever the case, by all the laws of probability roasting must have been the first method used, its discovery accidental.