Place sliced parsnips in a large bowl and drizzle with olive oil. Toss them around to coat evenly with oil. Transfer to a roasting tray and roast for 20 minutes.
Drizzle with honey and sprinkle over thyme leaves. Season with salt and pepper; return to oven and cook for an additional 15 to 20 minutes, or until the parsnips have started to caramelise and turn a lovely golden brown colour.