Hi @onlinebookshare and welcome to the Auth0 Community! 
From what I’ve gathered, you’re using the Authorization Core feature set and have managed to create some Roles under the ‘User Management’ tab in your dashboard and have even assigned those roles to users through the dashboard UI.
Now it sounds like you’re wondering where/how do I access those Roles? If attempting to access a User’s role info (or to assign roles for that matter), a solid place to do that would be in a Rule. Some examples of this can be found here:
https://auth0.com/rules/roles-creation
The above examples show how to assign Roles in your rule or to add Roles info to your tokens. They should also cover the use case I believe you specified regarding setting a default role to a user upon login. As this is a fairly broad answer, I may not have touched upon exactly what your issue is and I do apologize.If you have any specific issues that you need diagnosed we’ll be happy to assist further.
Best Regards,
Colin