I found this. It looks pretty safe..

Rhodiola Rosea Safety and Usage
Rhodiola rosea maintains an excellent safety profile when it is used as directed. A 100mg-300mg dose is recommended to promote healthy cognitive functions such as focus, attention, concentration, memory and mental sharpness. A 100mg-300mg dose is also recommended to relieve occasional nervousness, nervous tension, and anxiety or a depressed mood caused by everyday stress.

What are the potential side effects of Rhodiola Rosea?
Side effects are rare and have been documented as mild to moderate in clinical study. They may include headache, gastrointestinal discomfort, drowsiness, dizziness or sleep difficulty. In the event that you experience an adverse reaction, discontinue use of this herb. Rhodiola rosea does not cause withdrawal or discontinuation effects.

Is Rhodiola Rosea safe for children?
Clinical study data in children is limited and Rhodiola rosea should not be administered without the supervision of a professional healthcare provider.

Does Rhodiola Rosea adversely interact with prescription drugs?
Taking Rhodiola rosea in combination with prescription medications such as benzodiazepines, SSRIs, or SNRIs may cause drowsiness. If you are taking a prescription medication, it is recommended that you consult with your prescribing doctor before making any changes or additions to your current treatment plan.

What precautions should I take before beginning Rhodiola Rosea?

• • • Consult with your healthcare provider before beginning a wellness plan that includes dietary supplements like Rhodiola rosea
    • Do not take Rhodiola rosea if you are pregnant or nursing
    • Do not take Rhodiola rosea if you are currently taking a prescription MAOI
    • Do not operate vehicles or heavy machinery until you know how Rhodiola rosea affects you