Your product has a primary user store where the users/roles that you create using the management console are stored by default. It's default RegEx configurations are as follows. RegEx configurations ensure that parameters like the length of a user name/password meet the requirements of the user store. See Working with Properties of User Stores for more information of these properties.
When creating users/roles, if you enter a username, password etc. that does not conform to the RegEx configurations, the system throws an exception. You can either change the RegEx configuration or enter values that conform to the RegEx. If you change the default user store or set up a secondary user store, configure the RegEx accordingly under the user store manager configurations in <IS_HOME>/repository/conf/user-mgt.xml file.
The permission model of WSO2 Identity Server is hierarchical. Permissions can be assigned to a role in a fine-grained or a coarse-grained manner.
WSO2 Carbon maintains roles and permissions in the Carbon database, but it can also read users/roles from the configured User Store.