Combine the first 5 ingredients; stir well. Place roast in a shallow dish. Pour the marinade over the roast; cover and marinate in the refrigerator for 6 hours, turning occasionally.
Remove the roast from the marinade, reserving the marinade. Place the marinade in a small saucepan. Bring to a boil; reduce heat, and simmer for 5 minutes. Set aside.
Combine the currant jelly and 3 tbsp of the reserved marinade in a small saucepan. Cook over low heat for 5 minutes or until the jelly melts, stirring constantly. Set aside, and cool completely. This is your glaze to cover the roast with after it cooks. Refrigerate if you'd like -- just get it out about an hour before your roast is done so that it isn't too cold on your roast.
Place the roast on a rack in a roasting pan. Insert a meat thermometer into the thickest part of the roast, making sure it doesn't touch any fat. Bake at 325 degrees for 2 hours and 15 minutes or until the thermometer registers 160 degrees, basting frequently with the remaining reserved marinade.
Transfer the roast to a serving platter; brush with the glaze until thoroughly coated. Serve the roast with any remaining glaze.