> new

It's not all that new. Subdispatch with anonymous functions has been done before:

https://metacpan.org/pod/Web::Simple#DISPATCH-STRATEGY

As for readability, Roda kinda shoots itself in the code by not having any highlighting on that snippet, but generally yes, you want to keep dispatch trees to small apps. On the other hand, using P/WSGI apps you can stack apps inside one another, scaling trees without getting a moloch. Not clear on whether Roda supports that.