Hazelnuts???

[FantasticFox]

Does anyone have any experience using hazelnuts as an ingredient? We are planning a nut brown ale and would like to add in some fresh roasted hazelnuts (don't want to use any extract flavoring).
We previously used some toasted pecans for a stout, but the flavor was not very apparent.

Any information on quantity to use or any other advice would be greatly appreciated.

Cheers!