Preheat the oven to 425°. Drain the artichokes and pat dry. Cut each artichoke into eighths. Quarter the remaining lemon half and remove the seeds. In the bowl, toss the artichokes with the lemon pieces, garlic, olive oil and thyme. Season with salt and pepper and spread on a large nonstick rimmed baking sheet. Bake the artichokes for about 40 minutes, stirring occasionally, until golden and tender. Let cool slightly and discard the thyme. Coarsely chop 8 of the roasted artichoke pieces and reserve. Reduce the oven temperature to 375°.