Xfinity DNS and Roon

I have had problems in the past when streaming through Roon with skips and interruptions in music using Xfinity fiber optic service.  The Roon community monitor suggested that I change to a third party DNS such as Google.  My router is an Arris X5001.    I have tried to change the DNS on the router and the option is greyed out.  Trying to get a competent human to discuss my issue is impossible.

Does anyone know if it is possible to change DNS using Xfinity service?  Would a separate internet service just for HiFi be beneficial?

Thanks