Make the vinaigrette: In a small bowl, stir together the scallions, garlic, ginger, salt, lime juice, vinegar, and olive oil. Taste and adjust the vinaigrette with more salt, lime, or oil.
In a large bowl, combine the roasted vegetables, herbs, and most of the vinaigrette and toss to coat well. Taste and adjust, then spread out on a platter.
Drizzle with the remaining dressing and the thinned cream. Sprinkle with pepper.