Preheat oven to 475°. Put garlic, rosemary, sage, and salt and pepper to taste into a small bowl. Toss well to combine and set aside.
Push the handle of a long wooden spoon through the center of one end of the roast, boring a hole through the entire roast and to the other end. Remove the spoon and then push it in again through the same hole several times, moving it around in a circular motion to widen the hole to about 3⁄4".
Working with small amounts, push the herb mixture into the loin with the handle and your fingers, working first from one end and then the other, filling the cavity to the center. Put the pork roast, bone side down, into a deep roasting pan. Pat the roast dry, rub it all over with olive oil, and season generously all over with salt and pepper. Roast pork in the oven until golden brown (the roasting pan will smoke slightly as the fat drips into it), about 30 minutes. Reduce the oven temperature to 350° and continue to roast until the internal temperature of the pork registers 160°, about 1 hour more. Transfer the roast to a carving platter and carve into individual chops.
Serve each chop on a warm plate with pan juices and with white beans with sage, if you like.