It depends from what do you wish to achieve.
If you have no plugins or theme installed which added its own roles or user capabilities you may just use “Reset” button of User Role Editor. It will re-create roles from the scratch executing WordPress core code which WordPress uses itself during its installation.
Be careful with ‘Reset’ button and read this post before try this function:
This post contains other ways you may go to restore needed state of site roles.

You may to remove your changes manually. For example, if you created some role, assign to users with that role some of WordPress built-in roles, then you may delete your own role using User Role Editor. The same is correct for new capabilities you added using URE.