Cut rolls in half; place roll bottoms in 13x9-inch pan.
Cover with ham and Gruyere.
Spread cream cheese spread onto cut sides of roll tops; place over sandwiches in pan.
Mix butter, Worcestershire sauce, Parmesan and onion; drizzle over sandwiches. Cover with foil. Let stand 20 min. (You can make these sandwiches ahead of time and refrigerate overnight.)
Heat oven to 350ºF. Bake sandwiches, covered, 20 min. or until heated through.