Worried about root resorption after Clear Aligners. Any suggestions?

Root resorption is and will always be a risk of any orthodontic treatment. Dentists and orthodontists manage the risk by considering how long your roots are at the start and the risks in doing the treatment. A little resorption is considered an acceptable payoff for completing the treatment. 
This is why it is important to not have too many orthodontic treatments in the same teeth. Preventing relapse by wearing retainers is the best and most you can do. Also, when you notice any relapse it is best to act quickly to minimise the amount of corrective work that is needed. 
I agree with my colleague that the force should not be excessive, so ask your dentist. It is however a surprise to many people the discomfort of all aligner systems so do not expect a completely pain free system. 
Good luck with discussing this with your dentist and with a reputable system I do. It believe you should be too worried. 
Kind regards

Thomas Dey, BDS, MSc

What clear aligners are you wearing?  I know with ClearCorrect patients get a starter kit of aligners that are passive.  It gives the patient a chance to get used to them.  If they don't fit, then it is possible that the impressions were not accurate.  In the Houston area, we have dental imaging centers. These centers are capable of providing digital scans; so many of the inaccuracies of and the need for impressions are eliminated.  Root resorption typically occurs with heavy forces with the intention of rapid tooth movement.  Root resorption is a risk with all forms of Orthodontics.  Clear Aligners typically apply light forces with the intention of slow tooth movement.  Speak with your dentist about your concerns.