Preheat the oven to 400*F.
Slice the spaghetti squash in half and lay the open slices on a sheet pan lined with aluminum foil, skin side down.
Evenly drizzle the spaghetti squash with olive oil.
Evenly sprinkle the spaghetti squash with salt.
Roast the spaghetti squash for 35-50 minutes, depending on the size of the squash. The squash is ready when the insides are soft and fork tender.
Remove the squash and set aside until cool enough to handle. Use a fork to scrape the longs strands of squash from the inside, leaving only the skin behind.
Preheat the oven to 350*F.
In a large bowl, combine the spaghetti squash, mushrooms, butter, garlic and parmesan cheese. Toss to combine.
Pour the mixture into a large ovenproof casserole dish, at least 4QTs (9″x13″)
Top the spaghetti squash mixture with the shredded Italian blend cheese, spreading the cheese evenly.
Bake 20-25 minutes, until the mushrooms have cooked through and the melted cheese has lightly browned and is bubbling.
Remove and let cool slightly before serving.