Season the pork with salt and pepper. Wrap the bacon around the pork and tie with string. Tuck the rosemary here and there under the string.
Heat the oil in a large, heavy casserole dish over medium heat. Add the roast and brown it lightly on all sides, about 4 minutes. (Keep turning the meat so the rosemary won't burn.) When the roast has a golden color, turn the heat off and add the potatoes and garlic. Mix the potatoes, garlic, and oil well. Season the potatoes with salt and pepper.
Put the casserole dish in the oven and bake for 45 minutes. Baste the roast with pan juices while cooking. Check the roast for doneness by piercing with a knife. The roast is done when the juices that come out are clear and NOT pink.
Take the roast out of the oven, remove the string, slice the meat, and serve with potatoes and some pan juice. (I like mine with a salad and baked sweet potatoes.).