The barrel roll? I use a gamepad, but you can do this with a keyboard too. Apply full roll and full yaw or pitch(whichever is faster for your ship) and punch the burners. Since you're continuously changing your movement vector you will dodge almost all primary fire and most missiles. Being able to avoid fire while closing in with your target makes insane so much easier.
Despite what StarFox told you, just rolling while maintaining your movement vector is not a barrel roll.
This is because the AI aims at your lead reticle, with a continuous manoeuvre you will never actually be where your lead reticle says you will. Aspect missiles try to "lead" your ship as well, they will overshoot if you're changing direction continuously.
With the Atalanta you can also use the sidethrusters to push you outwards or inwards so that you can stay in missile FOV and fire your own heatseekers while avoiding enemy missiles.