We found this recipe on Bon Appetit and it looks perfect. You can skip all the info about creating the porchetta because we've already done that for you. All you have to do is cook it!
Refrigerate roast, uncovered, for 1-2 days to allow skin to air-dry; pat occasionally with paper towels. Let porchetta sit at room temperature for 2 hours. Preheat oven to 500°. Season porchetta with salt. Roast on rack in baking sheet, turning once, for 40 minutes. Reduce heat to 300° and continue roasting, rotating the pan and turning porchetta occasionally, until an instant-read thermometer inserted into center of meat registers 145°, 1 1/2-2 hours more. If skin is not yet deep brown and crisp, increase heat to 500° and roast for 10 minutes more. Let rest for 30 minutes. Using a serrated knife, slice into 1/2" rounds.
Here's the complete article: http://www.bonappetit.com/recipe/porchetta