A utility knife
Here are some tips, especially if it is 'stuck' to the floor:
It depends on what is under it. I had to redo my moms house, and the carpet was there for 50 years. The padding was a mess and stuck like glue. I had to rent a floor sander to get it all off. If you do this, be sure to use a face mask, it’s a messy job. I was lucky and she had beautiful wood floors under it all.
It should just roll up. Is it stuck to the floor?
Then you will need to scrape it off and possibly use a chemical to dissolve the glue. Just be careful and use protective gear!