This is especially important for drier climates, such as the southwestern states. Put them in a south-facing window if you have one. If you don't have that option, consider putting in a florescent light under one of your upper kitchen cabinets or wherever you have your plants. You can find these at nurseries or on the larger gardening websites. Water the roots, not the entire plant.
Rosemary plants are really picky about watering.
They like to be watered daily or a few times a week, but they don't like to sit in the water. I asked the plant department manager at Cub Foods how she got her rosemary to look so good. She does this daily to the plants in the store. Most potted plants only need to be watered weekly or twice a week, depending on the plant itself. Check out some indoor gardening books from the library and research the needs of your plants.