According to "The Reference Manual o Woody Plant Propagation" (a book I encourage all of you propagators to get) the seed requires no treatment.
However, I would probably try to grow a cutting from someone else's rosemary plant. Here are the basic instructions for that (this would go for lavender too):
1. Find someone with a plant you like & ask to take a couple cuttings
2. Cut a piece 3 inches long and remove the leaves from the bottom half
3. Prepare a ziploc freezer bag with about 3 inches of moist (not wet) sand in the bottom
4. Push the cuttings halfway into the sand and close the bag (perhaps leaving a small gap for air flow)
Note: if you have rooting hormone or some water steeped in willow bark you can dip the cuttings in this first to encourage rooting)
5. Put it in a warm spot that gets partial sun (make sure the sand doesn't dry out)
6. They
should form roots within a couple months. When they do transplant them to a well-drained medium and off you go.
Good luck!
Dave