Place all the ingredients, except pork and salt, in a shallow dish just large enough to snugly hold the pork. Add the pork and turn to coat in the marinade. Cover and marinate in the fridge, turning occasionally, for 4 hours or overnight.
Preheat the oven to 350 degrees F. Set the pork in a small roasting pan lined with parchment paper. Brush with the marinade; season with salt. Roast for 50 minutes, basting occasionally with the liquid in the pan, or until the centre of the pork at its thickest point registers 160 degrees F on an instant-read meat thermometer. Set the roast on a plate, tent with foil, rest 10 minutes, and then slice.
Note: Chipotle peppers (smoked jalapeno peppers) in adobo sauce can be found in cans in the Mexican foods aisle. Store unused peppers in a tight-sealing jar in the fridge for up to 1 month.