: My question is what are the pro's and con's of a recessed coaming.

Simple shapes are easier to bend than complex ones, so a recessed cockpit
is stronger and resists damage in three situations that can arise fairly
commonly. (1) you put a lot of weight on your cockpit rim entering or
exiting the boat (if you sit on the aft deck to slide in, then a recess aft
makes entry easier and the boat stronger where your weight is, which is just
what you need:); (2) you or your helpers pick the boat up by the cockpit
(commonest way for a single person to pick up an empty boat, or if three or
more people carry a loaded boat, one at each end and one or two either side
of the cockpit); (3) more of a whitewater consideration, but if you play
in waves or currents/tideraces and rocks, a two point pin with the cockpit
open to the pinning force can result in oil-canning where the boat collapses
around the cockpit. If you happen to be still inside, you will likely
be unable to exit which can, of course, be fatal ! The extra glass and the
shape of a recess make it much stronger.

If your foredeck is not so high that water never washes over it in a
headsea (and a foredeck that high is going to give you a lot of windage),
then when that wave washes over the deck and reaches a non-recessed
coaming, it will spray up right in your face. This means there is quite
an advantage in having a recess into the foredeck. Of course, a foredeck
hatch may have already done this, in which case the coaming won't make a
lot of difference !

As you have noted, a deep (and perhaps also long) recess aft makes
layback rolling easier. A recess may make it easier to lean forward to get
your paddle to the surface to start the roll.

A recess at the sides makes it a little less likely that water will get
under the spraydeck and into the boat when you are hit by a wave from the
side, as the wave doesn't hit the lower edge of the spraydeck directly.

: Are there any disadvantages?

Contrary to that last advantage, a recess at the side means that your
spraydeck is more likely to be underwater in a leaned turn, which will
let water in if it is at all loose - a good curve to the cockpit rim is
needed, since straight sides to cockpits inevitably result in looseness
of the spraydeck fit (tension along a straight line can't generate a
gripping force at right angles). This is more a disadvantage of a
keyhole cockpit than of a recess :-)

A deep recess which doesn't drain will also result in your spraydeck edge
being in water constantly, so you either have to have the recess shallow
enough to drain at some point (usually just aft of the widest point), or
you have to add a scupper at each side. For whitewater cockpits that last
is good, since an alloy bar across a deep cockpit scupper makes an ideal
rescue point to clip a krab. That's less of a consideration for a sea boat
as very few rescues involve recovery from a pin...

Andy