Oracle to PostgreSQL: Create type object
Although the syntax is different, you can achieve exactly what you want. 

You can create type by using the script below; 

CREATE TYPE tr_del AS (row_id varchar(18), pk_id integer);


Then your table structure should look like this; 

CREATE TABLE employees (
   department_id integer,
   any_field_name tr_del,
   ...
);


After that you can use it in the query like this;

SELECT
    (any_field_name).row_id AS last_name,
    (any_field_name).pk_id AS employee_id
FROM
    employees
WHERE
    department_id = 30;


Fiddle is here

You may want to read Composite Types section.