1) Cut open bread rolls.
2) Slice tomato, cucumber, cheese and salami.
3) Spread tomato paste onto bread.
4) Layer ingredients into roll.
5) Season to taste.

Variations:
Instead of tomatoes and cucumber, try sugar snap peas. Instead of tomato paste, try avocado. You can pre-makes these for day one.  I also often keep it simple on day one and carry in some cheese and bacon rolls or something similar from a bakery.

Make the most of fresh rolls while they last - the rest of the trip will be biscuits!