You're right, it would be good to replace the grates. Until you replace them, you can use foil. Butternut squash is really good when it's roasted. It's easier to peel if you microwave the whole squash for a minute. Then peel it, cut it up in chunks. The chunks are good grilled in foil packages with sliced onion and olive oil with s&p. The leftovers reheat well in a microwave.
P,S. Birds love the seeds, and an ice cream scoop works well to scoop them out,