Freezing Hazelnuts, before or after peeling and roasting

To prevent the vegetable from going 'off' in the freezer.

From answers.com:

Blanching is the scalding of vegetables in boiling water or steam. Blanching slows or stops the action of enzymes. Up until harvest time, enzymes cause vegetables to grow and mature. If vegetables are not blanched, or blanching is not long enough, the enzymes continue to be active during frozen storage causing off-colours, off-flavours and toughening. Blanching time is crucial and varies with the vegetable and size of the pieces to be frozen. Under-blanching speeds up the activity of enzymes and is worse than no blanching. Over-blanching causes loss of flavour, colour, vitamins and minerals.

I don't think it makes any tremendous difference. I'd probably lean towards toasting them whole first, then chopping just because the size will be more consistent so the toast might be a little more even.