It's all player facing. The roll players make covers an entire combat interaction and not necessarily a single strike from one character. if the result is lower than the enemy's score, the difference is the damage the player takes.
For example, if a DS 10 monster attacks my character, I roll a 5 plus 2 Brute, plus 1 from my sword. 8 total. 10-8=2 so I take 2 damage. If I had rolled an 8 or higher, putting the total over the DS 10, the monster would have taken damage.