Full-time, on-staff tabletop/pen-and-paper RPG writers with benefits are incredibly rare in the US.

I was told in 2000 there were more full-time astronauts in the US (149 at the time) than full-time, on-staff RPG writers. I suspect that was true at the time. There are fewer US astronauts now, and a lot more small companies with 1 or 2 people running it as full-time jobs, so whether it’s true now is going to depend on how you define things.

Getting on-staff at a game company as a creative of any kind (designer, developer, R&D, writer… titles vary by company) requires you to have a proven track record and a reputation for being someone that is easy to work with. In my opinion, nowadays the easiest way to get those started is by writing things for social media (one of the reasons I have a blog, for example), then work cheaply for small game companies, often for pdf-only or print-in-demand products. Hopefully you’ll get better, get more work, and come to more people’s attention. As your network of contacts spread and more people know about you, the size of company that is interested in working with you goes up.

The leap from that to an on-staff position is still a big one. I worked for Wizards of the Coast from 2000 to 2001, then was a full-time freelancer for most of the next 13 years before I got another staff job here at Paizo. You may have better luck than I did, or you may want to start your own publishing company, or begin a Patreon, or just do freelance work for several different companies, many of them smaller than Paizo.

Good luck to everyone who tries!