I have had people who tried to be friends and I had no desire to do the same, but I think it was mostly because I'm an RA and people wanted to "get on my good side" or something. In that case, I'd say to them that while I'm their RA and am concerned about what happens to them, I have to keep the relationship as professional as possible. That usually gets them to back off 9 times out of 10. Don't know if that's exactly something you'd be able to say, but you're not alone!
