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.