Well, suppose you the entity is called MyRoutes and that you are using Adapter template set, then it could be something like (approx code:
// fetch myRoutes
var myRoutes = new EntityCollection<MyRouteEntity>();
using (var adapter = new DataAccessAdapter())
{
adapter.FetchEntityCollection(myRoutes, null);
}
// add routes
foreach(var r in myRoutes)
{
routes.MapPageRoute(
r.RouteName,
string.Format("\{{0}\}", r.DisplayName),
string.Format("~/{0}.aspx", r.Url) );
}