I'm sure the Rhodiola does help with Insomnia, since it does help your adrenal glands.. I just wouldn't recommend taking it before you go to sleep because it stimulates your glands back into working, which could cause even more sleep problems. But overall, I am certain it helps with insomnia! =)
I purchased mine online, yes. It took me about a week to feel slight changes. More and more came after a few weeks afterwards. I usually take around 2-3 a day, alternating with Korean Ginseng. Hope I answered your questions thoroughly! =)