Luisa, I have this recipe for REC: Tuscan-Style Pork Roast which can serve as...
an example for you. The recipe says it takes about 2 hours for a 4 1/2 to 5 pound roast, but one of the reviewers wrote that it took another 45 minutes to reach 155F. The Food Safety & Inspection site says you should allow 20 - 30 minutes per pound, for a 2 to 5 pound pork loin roast, bone-in or boneless. Good luck with your roasts!
Tuscan-Style Pork Roast (Arista)
Gourmet - January 2001
Active time: 20 min Start to finish: 3 hr
Servings: Makes 6 servings.
garlic cloves
1/4 cup fresh rosemary
2 teaspoons fine sea salt
1 (4 1/2- to 5-lb) rib section center-cut pork loin, boned, meat reassembled with bones, and tied by butcher
Mince together garlic and rosemary. Stir together with sea salt in a small bowl and season with pepper. Rub 1 tablespoon garlic mixture all over pork. Beginning at 1 end of loin, make a 3/4-inch slit with a long thin knife through center of loin to other end. Stuff slit with remaining garlic mixture, pushing it through with handle of a long wooden spoon. Marinate at room temperature 30 minutes.
Preheat oven to 350°F.
Put loin, fat side up, on a rack in a roasting pan and roast in middle of oven until an instant-read thermometer inserted diagonally at least 2 inches into meat registers 155°F, about 2 hours. Let pork stand, loosely covered, 20 minutes.
Discard string. Separate loin from bones and cut meat crosswise into 3/4-inch-thick slices. If desired, serve bones cut into ribs.
Cooks' note: Roast may be rubbed and stuffed with garlic mixture 1 day ahead and chilled, covered. Bring to room temperature before roasting.
http://www.epicurious.com/recipes/food/views/104553