Some thoughts on going solo:
I have been a backpacker longer than a sea kayaker, and have done many solo deep-wilderness trips, such as in Alaska. Virtually all of my kayaking since starting a couple years ago has also been solo. I wouldn't have it any other way. There are things one experiences and things one learns about oneself solo in the wilderness that just can't be had in other ways.
The judgment real comes in understanding all the potential dangers and threats, and then finding the appropriate level of challenge. To restrict oneself only to that which is completely comfortable would miss the point for me; I want to challenge myself, but in a responsible way (I have a wife and kids). This isn't all about entertainment either; courage grows with exercise, and life often requires courage. We can develop this with things like kayaking solo.
I don't think one can underestimate how critical rolling is. We need to become rolling experts. I do serious rolling practice every time out. And one should really try to do this in a way that develops the skill for the kind of conditions where one would actually capsize. For example, find a friendly beach and a stiff onshore wind, and practice rolling in the surf. Roll both sides. Capsize in strange positions, or with the paddle in unusual positions. Hold your breath for a bit, and then capsize, then roll up.
I have found that while my rolling motions are "bombproof", the tougher part is to make my mind "bombproof". You have to train yourself to think about nothing else except good set-up, good roll technique...and NOT think about the waves, the wind, how shallow you are in the surf, etc.
Another critical point is dressing such that you would be safe for a significant period of time in the water temperature in which you will be paddling. This seems like an absolute must to me. keep a neoprene hood on deck when appropriate; makes a huge difference.
One critical piece of hardwear: a floating personal locator beacon with GPS. This is a sure way of 1) notifying rescue authorities that you are in a life-threating situation, and 2) your precise location. Can't imagine a more important tool. Of course, it's still a back-up. Paddle as if you don't have it.