freshly roasted hazelnuts and almonds are a taste which i've become slightly obsessive about, necessitating documentation of the perfect roasting method (separately however- they have different needs). the key to a good roasted hazelnut is a lower heat during roasting but not such a long cooking time that they dry out. they should be crunchy right through without being too browned on the outer, which makes them bitter. you want them to give up a little bit of oil on the outside so they smell and taste good.
pre-heat the oven to about 155°c and have the shelf in the middle.
put as many hazelnuts (with brown skins, no shells) as you can eat in one layer on a baking tray (without oil) and bake for 15-20 minutes. This is a guide only, it depends on your oven. Once the nuts start to give off a scent check to see if they're darkening at all. When they're done the papery skins will have darkened and shrivelled and the nut flesh will be lightly golden.
shake the tray once or twice during baking to even them out.
when they've cooled enough to handle rub the brown skins off either between your fingers (this is an easy way to eat large amounts of them before they even get to be part of any other dish) or wrap them in a tea towel and rub.
the nuts will get crunchier as they cool.