Certainly it's possible. I personally know dozens of people doing it. Check the job boards for full-time permanent RoR jobs. You'll see plenty, and not just from startups.
Is it really practical for someone to actually make a living programming with ROR? I live in michigan and I am wondering how to actually get a real job using ROR. Can anyone give advice on this topic? I have been in the IT field for over 20 years and have had jobs programming in Cobol and RPG. I am now in the IT security field and am wondering what it would be like to actually do ROR for a living. Is it just a thing for freelancers and people that are looking for part time work? thanks!!