Rosemary is very easy to root.
Over the autumn and spring I have had success with a pot in a cold greenhouse.
But always found summer is the best and I dib a hole straight into the ground to plant a cutting.
Rosemary much like a hedge cutting are very easy to propagate and grow quickly.
I normally take a 5-6 inch sixe cutting, remove all the lower leaves, dip in a rooting medium (I have always used Cinnamon) and pot up or into the ground. Water in well.