Preheat the oven's broiler to Low Broil.
Place 2 half slices cheese on each half of each roll.
Place hoagie rolls on a baking sheet.
Broil in the center of the oven until cheese is melted.
Meanwhile, heat beef consomme, French onion soup, and water in a saucepan over medium heat until just simmering.
Add beef until just heated through, 2 to 3 minutes.
Remove roast beef from soup, allowing any excess liquid to drip back into the saucepan; divide meat evenly among hoagie rolls.
Divide soup into 4 dipping bowls and serve sandwiches with jus.
