A roll rights the kayak while you stay in the cockpit. A wet exit gets you out of it. They solve the same problem in opposite ways, and the wet exit comes first: it's what you fall back on if a roll fails, or before you've learned one at all.
The ACA's Level 2 assessment describes a passing wet exit as calmly exiting the cockpit after a complete capsize, and marks panic or bailing out before the boat is fully over as below standard. That's the goal of practice: a calm, unhurried exit you've done enough times that it isn't a surprise.
Dressing for the water matters too, since a wet exit puts you in it. See what to wear kayaking and how to choose a life jacket for kayaking.