I read the Comp rules and it tells the 2 ways for an attack to get knockback, got it.
It also says that it applies to hit characters, got it.
My questions are these
If you use Force Blast that is auto knockback, no rolls, correct?
If you miss with a melee attack then KB would not occur, correct?
If someone generates KB with a Range attack, does the target still need to be "hit"

Thanks you

Correct, correct and yes the target still needs to be hit (and damaged).

Force Blast (Purple)
KNOCKBACK. // POWER: Minimum range 4. Knock back an opposing character
within range and line of fire 3 squares away from this character