Try to remove the shingles using a hammer. If it's too rotten, then you don't need a hammer. You can break it into pieces. I haven't done it before because I have built a tuff shed for my motorcycle a few months ago. I thought I would keep the bike outside, but my wife insisted on creating something to protect it from cold days. So, I have a new kind of garage for my beauty. And reading more about the necessity of having one Choosing or Building the Best Motorcycle Storage Shed: 5 Things to Consider I decided to make one from scratch. It took me few days, and the tuff shed was ready.
What do you consider "large"?
If it's really big and there's access, someone with an excavator with a thumb and a dump truck or dumpster can make quick work of it safely.