If you have a jar of artichoke hearts you can roast them quick and easily using a similar method as frozen ones. To roast artichoke hearts from a jar, drain them then dry them with a paper towel. If they are in oil, you can leave some of the oil to add back on if needed. Usually jarred artichokes are seasoned so no need to season them before roasting. If they are in water soak up all the water first then add a tablespoon of extra virgin olive oil, and a sprinkle of salt and pepper and coat them with your hands. Spread them evenly on a baking sheet and roast at 400 degrees F for 25 minutes. Flip and roast longer if needed.