I replied earlier in this thread, but thought that I would update, and specifically address your questions about rolling. My craft of choice is not technically a kayak, but a 7.5' waveski, basically a small surfboard hull that you sit on top of in a kayaking position. Control is through a lap belt and footstaps rather than thigh and knee bracing. It does bring up some of the same issues in terms of rolling and forward flexing. I got back on the waveski at about 4 months (though my doctor suggested 6 months), and had no problem with paddling and aggressive surfing. Forward flexing was much easier than before. According to my doctor, dislocation is not an issue from any of these positions. I did have some weakness during the hip flick phase in rolling for about the first year, but now that is better than ever.
I realize that it is not exactly the same, but from my experience with paddling, surfing, and rolling a similar craft, I do not think that you will have any problems once you are fully healed.