Debris Gambit says that red evades are white when near stuff, and gives a red evade action.

Aggressors can link barrel roll to (red) evade.

Does this mean an Aggressor with Debris Gambit can barrel roll closer to a rock (or to get around, or whatever) and then take evade as a linked action but white?

Yes.

Linked actions are considered "permission to do this action as well" not a single action to do two "actions" and count as one.

Thus, ANY form of a red evade will trigger "you just did a red evade?" events.