Combine salt, marjoram, basil, pepper, and garlic powder in a small bowl. Rub spice mixture all over the pork roast. Place roast in roasting pan, and surround with onions. Pour beer into pan, and cover.
Roast pork for 30 minutes in preheated oven. Uncover, and turn meat over. Continue to roast, checking for doneness every 30 minutes; add additional liquid if pan runs dry. Roast until internal temperature reaches 180 degrees, approximately 2 hours.