Rhodiola rosea side effects which are most common include restlessness, irritability, and insomnia. Take note that these are basically the same common side effects often experienced with the use of any mild stimulant though. If you take rhodiola rosea in high doses or combine it with another stimulant, the most severe side effects would be either a rapid heart beat, or heart palpitations.
I've read in anecdotal evidence that it's not advisable to consume rhodiola rosea when you know you have low blood sugar and won't be able to eat anytime soon.
Equally important here - you should always consult with an experienced naturopathic doctor or your physician before taking any new herbs or supplements, especially when you have a medical condition, in this case Type 1 diabetes.
I hope this helps.