OperationalError: FATAL:  role "odoo" does not exist`

This is a PostgreSQL error, saying that the database user odoo does not exist.

It probably means that your postgresql is using peer or ident authentication: instead for asking for user and password (postgres user and password, not your openerp one! they are different) it runs as the same user as the OS one. So, when you change the user you run the process as with sudo su, you are also chaning the user you're trying to connect to postgresql with.

"createuser odoo" creates an odoo user in postgres, but you probably created the openerp db with your "normal" user, so odoo has no databases associated with it.

The solution:

You should decouple your system user from your database user. You can, for example, use "normal" postgresql password authentication, that lets you specify which user you want to connect to postgres as.