First never put your own code in appstore modules. When you update the module you loose all your stuff. Put those custom made pages and microflows in your own module.
And indeed navigation is used for role based homepages. See documentation section 422 here: https://docs.mendix.com/refguide/navigation#1-introduction
your approach is against all best practices. Never allow anonymous user to create directly an account. In order to achieve this, the anonymous user requires to much access rights and thus potentially manage other accounts.
A better approach is is to create an non-persistable entity, which captures all the details the app needs to create an Account. Create the account in a microflow based upon the details specified in the NPE.
Also note that the anonymous user creating an account is actually loggedin to the app using a temporary account, which mendix manages. Thus this anonymous user != the account which is just created and thus the user must login using the NEW account, before the user will access the home page of the related role. As you modelled your microflow, the homepage of the anonymous user is displayed.
You need either to open a page with login widgets, to allow the user to login themselves or auto login them (which is a more complex trick; search on the forum, this has been answered many time already)