Hello, has anybody here implemented a way to hide admin dashboard (like redirecting to certain pages or showing 404 error page) for certain user roles and for those who are not logged in?

I think you can handle this with permission sets

That is a good idea. However, just to elaborate the details. You mean we can pretty much do anything we want inside the activate function on the permission sets? from what I understand, the permission sets can only be used just to restrict several models to be modified right?