Carefully, slice the parsnips in half lengthwise, or cut into ½ inch thick coins, or 2-3 inch long sticks.
Toss parsnips with oil. Bake about 25-45 minutes, until you start to see delicious caramelization spots on the parsnips. Time will depend on the size you cut the parsnips.
Toss with pesto just before serving. Alternatively, smear the pesto on the serving platter with a spoon, and arrange the parsnips over it.