The wonderful combination of ingredients make this Stromboli a winner!
Spray counter lightly with non-stick cooking spray. Combine rolls and roll into a 12 x 18 inch rectangle. Cover with plastic wrap and let rest 10-20 minutes.
Remove wrap and spread mustard over dough to within 1 inch of edges. Sprinkle evenly with ham and cheese. Press ingredients firmly into dough and carefully fold one long side into the center. Fold remaining side on top of the first and pinch edge to seal. Seal ends by folding over top 1-2 inches. Lift carefully onto a sprayed baking sheet and place seam side down.
Cover with sprayed plastic wrap and let rise 30 minutes. Combine water and soda and microwave to a boil. Remove wrap and brush top of Stromboli with hot soda water and sprinkle with salt. Using a sharp knife make score marks across top of Stromboli. Bake at 350°F 35-40 minutes covering with foil half way through to prevent over browning.