You do not need to peel the squash as the skin is thin enough to eat—do be sure to clean the skin well. Cut the ends off the squash and slice each squash open length-wise. Scoop out the seeds (using a grapefruit spoon if you have one). Slice each half into 3/4-inch thick slices. Place in a large bowl. Toss with extra virgin olive oil, Kosher salt and freshly ground black pepper.
Line a large baking sheet (17” by 11”) with parchment paper. Transfer squash slices in one layer to the baking sheet and set aside the large bowl.
Roast for 12 minutes and flip squash. Roast for another 10 to 12 minutes or until fork-tender and browned.
In a small bowl, mix Pecorino Romano cheese and sage.
Transfer the roasted squash back into the large bowl. Sprinkle the cheese-sage mixture onto the squash and gently toss.
Transfer the squash to a platter or dish. Sprinkle the squash with flaky sea salt. Serve warm.