One 2-lb. center-cut boneless pork loin roast
Kosher salt and freshly ground black pepper
1-1/2 Tbs. Dijon or grainy mustard
1-1/2 Tbs. honey
2 Tbs. roughly chopped fresh sage
1/2 lb. carrots (3 or 4), peeled
1/2 lb. parsnips (3 or 4), peeled
2 firm but ripe Bosc pears, quartered, cored, and stemmed
1-1/2 Tbs. olive oil; more for the pan
Heat the oven to 400°F. Lightly oil the bottom of a medium roasting pan or 15×10-inch Pyrex dish and set the pork in the center. Season the pork with salt and pepper.
In a small bowl, mix the mustard, honey, and half of the sage; spread on the top and sides of the pork. If the carrots and parsnips are thick (about 1 inch or larger around), cut them in half or quarters lengthwise so that they’re all roughly the same thickness (about 1/2 inch thick at their thickest part). Toss the vegetables and pear wedges with the1-1/2 Tbs. olive oil and the remaining sage, season with salt and several grinds of pepper, and arrange around the pork.
Pour 1/2 cup water into the pan and roast in the center of the oven until an instant-read thermometer inserted in the center of the roast registers 145°F, 30 to 45 minutes. (The cooking time will vary widely depending on the thickness of the roast; start checking early, and check frequently once the temperature reaches 130°F.) Transfer the pork to a carving board. (If the vegetables and pears aren’t fully tender by the time the pork is done, return them to the oven until tender, 5 to 10 minutes.) Let the pork rest for 5 minutes before slicing thinly. Serve with vegetables, pears, and pan juices.