How does Blazor Server route

There isnt a ton of documentation on the Blazor server app, and I know it uses SignalR, but the project does not contain a HomeController. So I am wondering how is routing down in blazor without it? Is it just base on Role/Policy authorization for pages and components?

Your question is not very specific, but the routing in a blazor app is done by Router component in the App.razor. The Router will scan the given Assembly for razor-components that have the @page directive. These razor-components are routable and will be able to get displayed by the RouteView-component.

App.razor:

<Router AppAssembly="@typeof(Program).Assembly">
    <Found Context="routeData">
        <RouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" />
    </Found>
    <NotFound>
        <p>Sorry, there's nothing at this address.</p>
    </NotFound>
</Router>

For authorization there is another RouteView-component called AuthorizeRouteView, but this requires that you wrap the whole Route-component with a CascadingAuthenticationState.

App.razor with auth:

<CascadingAuthenticationState>
    <Router AppAssembly="@typeof(Program).Assembly">
        <Found Context="routeData">
            <AuthorizeRouteView RouteData="@routeData" 
                DefaultLayout="@typeof(MainLayout)" />
        </Found>
        <NotFound>
            <LayoutView Layout="@typeof(MainLayout)">
                <p>Sorry, there's nothing at this address.</p>
            </LayoutView>
        </NotFound>
    </Router>
</CascadingAuthenticationState>

Basic routing is pretty well described in this Microsoft docu here. For auth with routing there is also a docu article here.