sorry but no, we are not redirecting to a specific page we are just redirecting to the root of the site which by definition happens to be the home page, ie http://yoursite/ or http://yoursite/default.aspx
trying to lookup what the lowest sort order root level page the user is allowed to view is not something I want to build in. We generally don't look up user permissions in the database, we just check the current page allowed roles against the user role cookie, doing that in the database would be much less efficient.
This is not something that has been requested before and it seems like a niche need to me. Its the kind of thing one might do if one were building a social networking site you might want to redirect the user to his own page but mojoPortal is specifically not for that.
My advice would be to instead think in terms of showing or hiding things on the home page based on roles. Say the home page view permissions are for all users, therefore all users can get to the url for the home page, but you add instances of Html content features on the page with more specific roles (view roles on the content instances) they will not be shown if the user is not in an allowed role, therefore you can taylor the home page content by roles.
Best,
Joe