Recent studies have been reporting a potential association between rosacea and autoimmune diseases like MS, Parkinson's. How do I not stress about it?

Health care. You heard correctly BUT the studies are small, based on some unsubstianted self-reports of the other diseases and says NOTHING about causality. There was suggestion that worse rosacea had a higher link and that good Tx can avoid worse rosacea - so, find and follow good Tx as well as maintaining a healthy lifestyle and that includes mgmt of stress! Seek a therapist you trust to learn those skills!.