Welcome to the forum, Linzi.
You may have done what I did, when I first grew rosemary, which is what I read back then, and many still say now - that is
let the pot dry out between waterings. As soon as that would happen, the plants never came back. They would begin yellowing, and slowly dry up, despite being watered again. That happened to me twice, after which I never allowed them to dry out, and they didn't die after that. However, I also discovered that rosemary becomes rootbound very fast. So I started keeping it in the garden, and, come winter, when it gets below 20°, I covered it, and when extremely low, I put a heater under the cover.
My outdoor rosemary died this year because the cover blew off, and I was physically unable to go out to re-cover it. So this season I ordered some from Richter's, the
Hill Hardy variety, which they say may be more cold resistant than
Arp variety, which I have tried, but it didn't have the same flavor as most rosemary. So I ordered 3 of these, and put one in a 4 gal fabric pot, which sounds like oversize for such a small plant, but, as I said, they got rootbound quickly, when I tried them years ago. It is going nuts in that pot, compared to the ones in the ground, probably 3 times the size. This was planted a couple weeks into May, starting with about a 4" plant. You can judge the size from the milk crate it is sitting on:
DSCF0769 by
pepperhead212, on Flickr