Combine soup mix, broth and beer in a bowl and stir until the soup mix is dissolved. Pour over roast and place onions around it.
Bake for 2 to 3 hours, basting frequently, or until beef is tender and looks stringy when pulled with a fork. If roast starts getting too crispy, cover pan with foil or lid.
Slice meat thinly and serve on rolls.
Serve juices in individual cups or bowls to dip sandwiches into.