Roast the carrots: Preheat the oven to 500 degrees F.
Cut the tops off the carrots, leaving about 1 inch of the stems still on. (Reserve the carrot-top greens for the pesto and garnish.) Cut the larger carrots in half lengthwise and leave the smaller ones whole. Place on a large rimmed baking sheet in a flat, even layer. Drizzle with a good amount of olive oil and sprinkle with salt and pepper. Roast until lightly charred and tender, but not mushy or falling apart, 10 to 15 minutes. Halfway through roasting, shake the pan so they roast evenly.
Meanwhile, make the pesto: In a high-powered blender, combine the carrot-top greens, parsley, pistachios, olive oil, chives, salt, pepper, garlic, lemon zest and lemon juice. Blend on medium-high until combined but still chunky. If it looks too thick add 1 to 2 tablespoons oil to loosen.
To serve: Place the roasted carrots in a shallow bowl, dish or platter and drizzle with the pesto, chopped pistachios, tahini and carrot-top greens. Serve immediately.