Preheat the oven to 450F. Line a baking sheet with parchment paper. Add fennel, olive oil, and ½ teaspoon salt to the baking sheet and toss to coat. Bake for 15-20 minutes, or until tender and charred in spots.
In a medium pot, add the quinoa and 1 ½ cups water. Bring to a boil, then reduce the heat to low and simmer, covered, for 12 minutes or until cooked through and water has evaporated. Fluff with a fork and set aside to cool off.
In a large bowl, whisk together the oil, vinegar, mustard, remaining ¾ teaspoon salt, and pepper. Add the quinoa, fennel, celery, and herbs to the bowl and toss to coat. Taste and add more vinegar or salt, if needed.
Serve topped with hazelnuts, goat cheese, and more black pepper.