@Andrew1, we have a new “Savings Budget” dashboard you can add to your Foundation template that offers “rollover” capability, but it is not the same Envelope (Tiller) Budget capabilities found in the Tiller (soon to be renamed “Envelop Budgeting”) add-on.
We did a demo of this in a community webinar a few weeks back if you want to see it live in action before playing around with it.