type of hazelnut?

Agree with Lori about not using salted hazelnuts and for same reasons.
But if you have roasted ones on hand, you could use those (for good flavor) and reduce the frying time to avoid a burnt, dried-out result.

You would want raw hazelnuts to start with, because you are going to fry them to infuse the oil and bring out their nutty flavor. You will also be salting them after frying. If you started with already roasted and salted nuts, the additional cooking would leave you with burned and overly salty nuts, and no tasty infused oil for the recipe.