ExRx.net

... how does it affect the nutritional value? Fatty acids, fibers etc.? Does it change it enough to matter?

I would think there would be a minor loss of antioxidants and an improvement in digestibility but simply soaking may achieve that end. High heat can upset the fats. If you roast your own, you can avoid adding salt and vegetable oil. Roasting does make them taste better.

I do roast them myself, they taste much better. I mix flaxseed, pumpkin seeds, sunflower seeds and chopped almonds, hazelnuts, pecans, walnuts... whatever I have in the house, and eat with plain yoghurt. Good stuff!

I have a great big book of nutritional values at the office I'll look at if I get a chance and remember. For the time being:

http://www.xomba.com/raw_organic_nuts_vs_roasted_which_better_you

Though this looks like a hippie site.

I did look at for peanuts just out of curiosity:
http://www.nutritiondata.com/facts/legumes-and-legume-products/4355/2

and the nutritional data wasn't that different, though there was a decrease in calcium and iron when roasted.

For what it is worth - cashews are poisonous raw.

mmmmmm delicious poison