hello,

can i modify defence results if i don't roll defence dice... for example protector ability (or survival istincs) on the bantha rider ?

Yes.

You are adding symbols to the defense results from both the defense die/dice and other abilities.

Just like the attacker is adding symbols from the attack dice and attack abilities.

A few attack-related rules and the order of ability resolution: Ability Resolution Order During Attacks

Anyone can have defense results, even if the didn't roll dice.

In most cases those defense results would be nothing, but some characters have innate bonuses (like Luke, or Bossk etc)

Others may have command cards or special abilities in certain situations.

12 hours ago, emp1975 said:

protector ability (or survival istincs) on the bantha rider ?

Keep in mind that protector doesn't work on all spaces of the Bantha. That's an easy one to overlook as well.