How to remove globally user roles in WordPress

So I have read a lot of Websites on how to do it but I would like to use it globally so if I use a different theme it should reflect the security roles that I have put in place and not the default once.

Afterwards I like to create another role for registered user that can only view the site just like guest can do but there are registered this will help me to assign additional roles for example forum/memberships etc… where I can assign them later or automatic.

As always I thank you all for the help