It depends greatly on what you're attempting to do with the language. Ruby is a fairly straightforward language that can easily be used in a regular imperative manner and that comes with a massive amount of libraries and frameworks (most notably Rails).
If you want to develop standard business information systems and/or websites, there's not a whole lot of computer science required to get extremely far. Most of it will pop up when a site you've developed becomes very popular and performance and scalability becomes an issue. Up until then, what you'll need to learn are programming practices, design patterns, testing tools, modularity approaches, etc. Nothing that is very theoretical.
There are basically two reasons you might need to dive into computer science concepts to get further:
- You want to implement all kinds of algorithmic functionality (from sorting to indexing, etc.) yourself or want to write an application focused on these kinds of activities.
- You want to use everything Ruby has to offer and use internal DSLs, metaprogramming, full functional style, etc.
Both I would say are entirely optional until you've been working as a Ruby developer for a couple of years and really want to go further.
At the same time, I am a firm believer that a serious, in CS-grounded approach to software engineering is the only way to really excel in your field. But if you desperately need a job now, forget about that (but not indefinitely, because I don't want to be hired a couple years down the road to maintain your stuff :))