Preheat the oven to 400F/200Line a baking sheet with parchment paper.
Toss the grapes in a bowl with the olive oil and a pinch of the sea salt, then spread the grapes onto the baking sheet. Roast until crinkly and lightly caramelized, 15 to 20 minutes. Remove and cool.
Lightly toast the Aegina pistachios in a dry nonstick skillet over medium heat, shaking back and forth for 2 – 4 minutes, until their aroma starts to bloom. Remove from heat immediately.
Dip the rusks in the orange juice and remove immediately. Break the rusks in half or thirds. They will probably break apart into amorphous chunks, which is exactly what we want for this salad.
Gently toss the arugula, grapes, pistachios, half the crumbled feta and rusks together.
Whisk all the ingredients for the dressing together until smooth and emulsified. Toss the salad with the dressing and plate on 4 individual plates. Garnish with the remaining crumbled feta and pink peppercorns and serve.