Is Invisalign a Risk for Teeth That Have Small Roots?

While nothing is without risk, the odds are better with invisalign in this situation. Slow and steady will not usually make the short roots shorter, but they still COULD. Root resorption is normally associated with trauma to the teeth or genetics, but moving too fast CAN contribute.
As long as the periodontal condition is stable, you should be fine.

While there is a risk of root resorption generally associated with small roots, there have been no documented cases of root resorption occurring with Invisalign treatment, with over 1 million patients. Align posulates that forces are so controlled, that few cases of resorption occur.
Still, it is a good idea to discuss this with your orthodontist, particularly if the existing short roots are already allowing mobility of the teeth prior to treatment.
Good luck!

If your roots are short due to previous braces etc then you can have your dentist slow down the tooth movements with Invisalign. But generally its such a gently tooth movement that we dont normally see any root shortening during the treatment.