Vladimir,
I’m still working on this issue. I see in the database that the wp_usermeta table has some odd meta keys, such as aa_user-settings, aa_3_user_level, aa_4_capablities, etc. The prefix on my database is wp_ (wordpress default), not aa_. Is there a reason that there would be some keys prefixed with aa_? Or could this be why my user roles are missing?
[edit] I also see an aa_user_roles key in my wp_options table. That’s the options for the root site. Is this correct?