postgresql roles what they are and what you can do with them

The following link provides access to an excellent blog on the subject.

https://www.crunchydata.com/blog/postgresql-defaults-and-impact-on-security-part-1

see pg_has_role

select pg_has_role(<role-name>);  -- returns true of false

Assuming a Role

Gaining access to a given role may only be gain by “using” that role directly, which can be accomplished one of three ways:

1.) SET ROLE to switch that role

2.) SET SESSION AUTHORIZATION

3.) Your current role has inherited access to the role in question

How is this impacted when you are using AWS RDS Postgres or AWS. RDS Aurora with Postresql option?