Are you process-oriented or product-oriented?
It seems like job advertisements for Rails developers tend to fall into two general categories. In the first one, a company is looking for a Rails developer who also is adept at system administration, deployment, and tasks related to application performance and monitoring. The second type of job ad looks for a Rails developer who is also capable of front-end code, understands User Interface design, and has an appreciation of User Experience.
(There is also a third category of job ad - the one that looks for a Rails dev who can do all of the above, is a professional ninja, a former pirate, and an aspiring superstar. I won't be talking about that kind of ad here).
To me, this is a symptom of a company being process-oriented versus product-oriented. Granted, with a large development team a company will have back-end developers who naturally gravitate either towards the sysadmin end of the production spectrum or the designer end. However in a small, entrepreneurial company it is important for everyone involved in production to have a product-centric focus. This means that it is more valuable for a back-end dev to have a flair for design, copywriting, usability, Information Architecture, packaging, and marketing, than it is to have sysadmin experience.
If you're a small team, tight on budget, and eager to put a product out, hire a back-end dev with strong conceptual and business modeling thinking who also has a marked interest in User Experience. For system administration, monitoring, scaling, and optimization hire an experienced sysadmin, part- or full-time, who will be glad to help you with what he likes to do best.