As a full-time paid RA, should I get co-authorship on a paper that I have written? I am working as a full-time research assistant at a university. I recently wrote a paper almost entirely independently. The contribution of the professor I work under was limited to telling me the topic that the paper is to be written on, and providing minimal inputs on the drafts (things like changes in grammar, or the inclusion of another aspect of the topic).

Now he is presenting the paper at a conference, and is listed as the sole author of the paper. As far as I know, I am not even noted in the acknowledgements. Am I incorrect in thinking that I should be listed as at least a co-author on the paper?

The only reason I am confused is because I am paid for my work at the university. However the work that I have done on the paper goes far beyond my professional responsibilities. Furthermore, I was hired to work on a completely different project altogether, but am helping the professor with most of his research.
If you have written the paper, you certainly have the right to be at least a co-author. In fact, from what you said, it seems to me highly dubious that your professor should a an author at all.

Being paid as a RA does not waive your right of getting credits for publications you wrote. Your professor is also paid by the university.

EDIT: 

If you would like to talk to your professor about this, I'd suggest that you talk politely. To be honest, I don't know how to do this, but I am sure this is important (and possible).

Thanks to Captain Emacs for their very valuable advice in the comment.