Full sun outside is one thing, sun reflected through glass is quite another! Yes, you're cooking your rosemary by putting it near a window. Touch that window some time during the summer and see how your hand feels! It will be a bit like touching a glass dish just removed from the oven. Not surprising your rosemary is showing signs of discomfort.

When you take rosemary or any other herb from inside to out, you have to do it slowly so it can adapt to the change. You've basically given it a little sunburn. If you put it in part-sun, then slowly introduce it to full sun, it will be okay. Just give it time to recover. Don't fertilize while it is recovering. Too much shock all at once. Good luck!

When I said I grew it in full sun last summer, I meant outside - I only brought it in for the winter. It was in about the same spot.
I did harden it off with my veggie seedlings - is there anything else you can think of? Or is rosemary more touchy about being moved outside? I will move it over to the east side of the house - it's the only place we really get any shade - it certainly couldn't hurt it.

Rosemary likes full fun, so it will be happiest there eventually. Put a larger pot nearby so that it is partially shaded during the hottest part of the day - that will be quite a good way to harden it off. After a week or two, the larger pot can be moved away - the plant will no longer need protection.