How to connect through multiple databases's users/roles

Hi. I'm trying to authenticate users against the database's user/roles
in PostgreSql, instead to use in 'database.yml' an almighty user (like
'root').
Can I use 'ActiveRecord::Base.establish_conection' method to do that?
And is this related whit ActiveRecord::Base.allow_concurrency = true and
ActiveRecord::Base.verify_active_connections?
I know about issues related with this point (Katana Suicide
Concurrency), but I really need connect each system's user as single
user/role. I think this must be able to do. Thanks.