Moby Dick wrote:
Looking through the local sports magazine (Boulder, Colorado), I see
lot's of "roll classes" for whitewater kayaks. Do sea kayakers need
this, too.

Yes, they do, especially when paddling in cold water. Unfortunately,
most sea kayakers never bother to learn to roll, which is really
short-sighted. Rolling is not only an important safety skill, but it's a
"gateway" skill that makes it much easier to learn more advanced
edging, bracing and paddle strokes. Knowing how to roll can result in
dramatically improved boat handling ability overall.

I know what rolling is -- seems to me that if a sea kayak
is flipped due to a wave or something, it'd be good to know how to
roll back up. Or is just getting out of the kayak sufficient?

Although knowing how to wet exit is obviously important, it should be
regarded as a last resort, not an integral part of one's safety
strategy. A good analogy might be falling while skiing. Anyone can stop
on skis by simply falling down (and beginners are often taught to do
so), but it's not the first choice or the best choice, it's what you do
when all else fails.