It depends on where you live. In Kansas, if left outside, rosemary dies
in winter unless it's particularly mild & the plant is very
well-mulched. Wintering indoors, I found that rosemary does okay so
long as it's kept well away from forced-air heat ducts. My plants
winter well in a cool corner of the kitchen, behind french doors facing
west (indirect light). My kitchen has no heat ducts, & it's the only
room in the house where they will live in winter. The french doors
happen to be opened several times a day, & the plants seem to like the
moister, cool air - so long as they don't sit in freezing air for long
periods. Just don't let them dry out.