I made a rosemary topiary and had it for many years until I tired of it and gave it to a friend. I kept it outdoors in summer and indoors in winter. (Zone 5) In spite of some garden books that said to grow it on the dry side, I always kept it well watered or the branches would dry up. It doesn't take much work to maintain its shape with an occasional trimming and it will make a nice addition to your container plants on your patio. Fertilize it when you do your other containers. In addition to smelling great, it also may surprise you with lavender blooms.

It should be fine if you let it go back to a more natural shape though it could go through an awkward stage. Upright rosemaries are really easy to maintain, just trim them like you do your hedges. Trailing rosemaries can be let loose to ramble with just a snip or two if they get out of hand.
I agree with Barbara about watering. Rosemary doesn't like to get bone dry; they turn toes up and die quickly if they're in a container especially. I keep mine on the dry side of moist and they do fine. If you keep yours in the window, you may find that it will get nectar and petals all over the glass when it flowers.

Veronica

Most growers of Herb plants in general do not add lime to the growing mix or top dress their container plants as the herb plants need a raised ph.I use pellett lime for this and it does as much for plant growth/health as a shot of water soluble fertilizer.