Details about existing roles and users in azure sql database I would like to get details of all users existing in a sql server DB and the respective roles they are part of and the permissions granted/denied for the a role/user.

what is the best way to get this details?
If you are talking about Azure SQLDB or Managed instance you can use this script:

SELECT role.name AS RoleName,
       member.name AS MemberName
    FROM sys.database_role_members  rolemember
JOIN sys.database_principals AS role
     ON rolemember.role_principal_id = role.principal_id
JOIN sys.database_principals AS member
     ON rolemember.member_principal_id = member.principal_id
     order by 1

I hope this helps.