Preheat oven to 350 degrees. Place hazelnuts on a baking sheet and roast for 5 to 7 minutes until fragrant and skins start to split and peel away from nut. Place hot nuts in the middle of a kitchen towel and gather it up at the ends. Rub nuts roughly in the towel to remove skins (if some skin remains, that's okay).
Meanwhile, in a large salad bowl, combine garlic, salt, vinegar, lemon juice, and oils, and whisk. Add lettuce, endive, and arugula, and toss to coat. Add nectarine and hazelnuts; toss gently.
If you assemble the salad ahead of time, coat the nectarines in lemon juice to prevent browning. Dress right before serving.
You can also use peaches or apples in place of nectarines, and radicchio instead of red endive.