Here is my limited research on this :
I have been taking it for 3 1/2 weeks now and feel that it is worth you all looking into and doing more research with me
I decided to start off with Contraindications for using it, anything thing listed below is a RED Light ...Don't Use IF:
1. pregnant or nursing ....& don't give to children
2. do not take if you are taking an MAOI (it acts as one)
3. If you are bipolar or have manic depression
4. If you have sever kidney or liver disease
5. If you have low blood sugar (take with food) don't take if you
won't be able to eat within 30 min after taking this herb
6. Do not combine with caffeine
7. Take in am...it may interfere with sleep
Possible side effects: insomnia, irritability, mild jitters, restlessness, vivid dreams. It can restore menses. High Doses can cause: heart palpitation, rapid heart beat, or a panicky feeling.
Start with a small dose and stay small...works as homeopathic (less is more)

Things Rhodiola rosea has been used for:
Treatment of colds, anemia, headache, cancer, infertility and erectile dysfunction,leukorrhea, and to strengthen the heart muscle. It promotes energy and stamina and mental performance (memory , etc)
As an anti-oxidant, it protects the nervous system from oxidative damage from free-radicals. It reduces stress related chemicals in the body and improves MOTOR COORDINATION. It is an anti-inflamatory.
One site said...Helps to rebuild dopamine.
Starting in the brain stem it promotes release of norepinephrin, serotonin and dopamine and enhances the effects of these neurotransmitters on the brain by increasing the permeability of the BLOOD BRAIN BARRIER.
It increases ATP . It enhances thyroid function without causing hyperthyroidism. Helps the thymus and adrenal glands to function better.
I started out taking 400mg Swanson Rhodiola rosea on Dec21st. After exactly 2 weeks ..noticed that I didn't need as many doses of fava tincture (my homemade l-dopa supplement from fava plant). The next day, I didn't require any. Certain days needed one dose or more . After 17 days had 2 very short episodes of heart palpitations and decided to cut back on dose. I am now emptying 1/2 a capsule into my cereal in the morning and saving the other half for the next day. This seems to be working well (approx 200 mg daily) I feel a tincture would be better for controlling dosage and probably 100mg a day may give good effects good effects.(possibly even 50mg)

Hope this will inspire some of you to more research on this herb. God Bless