Preheat oven to 400 degrees.
Use a sturdy vegetable peeler to peel both squashes.
Cut squashes in half. Remove seeds and membranes and discard.
Cut squashes into 1" cubes and place in a single layer on a cookie sheet. If crowding is an issue, use two cookie sheets.
Drizzle with olive oil and sprinkle with salt and pepper. Stir to coat.
Roast for 45-60 minutes until edges brown and caramelize.
Melt butter in a small sauce pan or skillet.
When butter comes to a foamy simmer, add sage leaves. Cook 1-2 minutes and then flip with a fork.
Cook an additional 1-2 minutes. Remove from butter and place on a napkin to drain and dry. Sage will crisp as it drys.
Continue cooking butter, swirling often, until the color deepens to a golden brown and then remove from heat.
Place roasted squash in a serving bowl. Top with either whole or roughly chopped crispy sage and drizzle with spoonfuls of the brown butter. Garnish with flake sea salt if desired.