I second that, I use several layers of old thick blankets, comforters and sheets that I get from a second hand thrift store!
you can put the sheet as the top layer and usually you'll only need to wash that one, the lower layers may not get wet that often, but they can discourage rats from getting down to the carpet to possibly chew it up
I had that happen, and oh boy can they chew fast LOL
You can also try an area rug over the carpet, if you're not going to use the whole room. Or even if you are, the more protection the better lol
I had my own carpet cleaner but it didn't help when the little buggers started pulling up the carpet fibers
lucky for me it was a very old carpet so I wasn't charged when it was replaced by the landlord, however I no longer let my rats free range on the new carpet
They have two play tables pushed together plus my bed, and sometimes the bathroom. Not as much fun as having a whole room but it will have to do.
for dig boxes you can use aspen shavings, you can use eco bedding (paper shreds) and /or you can use coconut coir fiber, and probably other things I don't know about.