Cardboard pet products are considered safe for chins to chew on,but cardboard should not become part of chins diet( if they ingest really small amounts of paper, it usually does not cause problems). However if a chin ingests lots of paper( like 1 toilet tube a day) it can cause obstruction and may also reduce the amount of hay/pellets a chin eats. I would not put any cardboard items in my chins cages. I used to put some cardboard tunnels during playtime because chins are supervised.
Commercial cardboard (toilet paper rolls) may have wax or glues or chemical pre-treatment. I do not think they are safe to put in chins cage. And it does not wear down their teeth enough, it's better to offer safe wood chews, pumice stones, different types of hays. Just my opinion.