Preheat oven to 450F degrees. Split rolls in half (lengthwise). Put on baking sheet and set aside.
In a medium bowl, combine ground beef, crushed crackers, egg, onion, milk, 4 tbsp. ketchup, Worcestershire sauce, dried thyme, garlic powder and salt and pepper.
Top each bun-half with meat mixture (spreading it out evenly amongst all the buns.)
Spread additional ketchup on top of meat mixture (as much or as little as you like).
Put in oven and bake for about 15-20 minutes (until meat registers 160F degrees).
Take them out and add shredded cheese on top.
Bake for an additional 2-3 minutes until cheese is melted.