We actually have a whole story full of pork loin ideas here: http://www.bhg.com/recipes/pork/roasts/pork-roasts/
For a simple recipe to try tonight, this one is a good option:
1. Combine 2 tablespoons of the mustard and the sage; spread over surface of meat. Combine vegetables and margarine or butter; toss to coat. Place the roast, rib side down, in a shallow roasting pan. Insert a meat thermometer into center of roast. Arrange vegetables around roast. Roast, uncovered, in a 325 degree F oven for 1-1/2 hours or until the vegetables are nearly tender.
2. Combine remaining mustard and syrup in a saucepan. Bring just to boiling. Drizzle over vegetables; toss to coat. Continue roasting about 30 minutes more or until thermometer registers 160 degrees F and juices run clear. Remove roast from oven. Cover roast with foil; let stand 10 minutes before carving. Just before serving, remove vegetables from pan juices with slotted spoon. Makes 6 to 8 servings.