Preheat the oven to 400 degrees. Toss the butternut squash cubes with olive oil, salt, and black pepper on a baking sheet.
Roast the squash for 25 minutes until the edges turn golden and the pieces soften. Remove from the oven and let cool slightly.
Place the cheddar cubes, gouda slices, and brie wedges on a large board, spacing them apart to leave room for the squash.
Add the salami slices in small piles near the cheeses. Scatter the walnuts and apple slices around the edges.
Arrange the roasted squash cubes in clusters across the board to create the pumpkin patch look. Fill in gaps with baguette slices.
Top the squash clusters with pumpkin seeds and tuck rosemary sprigs between the cheese and squash sections.