Pre-heat the oven to 425 degrees F. *You could peel the citrus if you choose, but the slices hold together better if you leave the skin on while roasting. Line a rimmed baking sheet with parchment paper. Line the citrus slices in a single layer on the baking sheet. Drizzle honey or olive oil on the citrus and sprinkle on the salt, and pepper, is using. Roast the citrus until lightly charred in spots and the slices are starting to caramelize, about 10-15 minutes.