Preheat the oven to 450°F. Add the grapes to a baking sheet lined with parchment paper. Drizzle with a little olive oil and sprinkle with a pinch of salt. Roast for 35-45 minutes. Remove from the oven. When cool enough to handle, slice the grapes in half. Set aside.
Combine the shallot, honey, vinegar and lemon juice in a small bowl and whisk to combine. Slowly add the olive oil, whisking until combined. Season with salt and pepper. Set aside.
Place the arugula and friseé in a large bowl. Add the grapes, Jerusalem artichokes and onion and gently mix to combine. Toss with the vinaigrette. Place on a platter or individual plates. Serve right away.