Yes sniffing a bit of rosemary essential oil or applying some rosemary essential oil to your skin or in a diffuser can help you fall asleep.
Whenever I have trouble falling asleep at night I will put some rosemary essential oil into an essential oil diffuser and turn the diffuser on and turn the diffuser on 10 minutes before bed so that the rosemary essential oil will disperse into the air in my bedroom.
Then when I lay down in bed I start drifting off to sleep within 15 minutes of inhaling the rosemary essential oil.
The rosemary essential oil stimulates your brain somehow and triggers sleep and it does work for me but your results may vary.
But it's certainly worth a try if you're having trouble sleeping.