As a Ruby on Rails (Junior) Developer, I think it also depends on what you want to accomplish.
Now concerning job requirements (for most RoR Devs), I usually see other languages such as JavaScript, JQuery, CSS, HTML, SQL, and I believe a moderate knowledge of those languages can land you a pretty decent job. (Full-Stack Dev).
If your main focus is on Front-End you definitely want to know JavaScript, JQuery, CSS, HTML.
Rather, if you’re focus is Back-End you want to focus more on Ruby, Rails, SQL, APIs.