Our current plan is to start the meeting with features discovery, then
jump into roles discovery as a team.
We plan to allow the team members to write out roles on index cards
and we can then pick the common ones.

My question is, how do I make sure we are not missing important roles?
Should I be considering personas as well, such as a user who is over
25? Or should it be limited to a user, or an admin or a visitor?

The second question I have is that it that it seams like roles need to
be extracted based on the features but the stories are what seems to
bring the roles out. In other words, a feature like "Implement user
search" does not seem to aid role discovery as much as a story... " As
some role need to be able to edit find users so that I can edit their
accounts".

Thank you!