Preheat the oven to 400°. Spread the parsnips on a large rimmed baking sheet and toss with 2 tablespoons of the olive oil. Season with salt and pepper and roast in the bottom third of the oven for about 25 minutes, or until lightly browned on the bottom and tender.
Meanwhile, bring a large pot of water to a boil. Add salt and then the kale and cook until just tender, about 5 minutes. Drain and then squeeze out the excess water. Coarsely chop the kale.
Heat the remaining 3 tablespoons of olive oil in a large skillet. Add the garlic and cook over moderate heat until golden, about 2 minutes. Add the scallions and cook over moderate heat, stirring, until softened, about 2 minutes. Add the kale, season with salt and pepper and cook, stirring, until heated through, about 3 minutes.
To serve, add the parsnips to the kale and warm through over moderate heat.
Make Ahead: The kale and parsnips can be prepared through Step 2 and refrigerated overnight. Let return to room temperature before finishing.