A small rolling suitcase is fine to carry on (please carry it on because if anything breaks/leaks, you can ruin someone else's luggage) and you can put your beverages in there. We put the water bottles and wine in our totes/backpacks to carry on, so it doesn't seem like the actual contents were the issue.
DCL also removed a small steamer from my mom's suitcase (which she shouldn't have brought, but didn't know it wasn't allowed) which she was able to pick up at lost and found in the terminal after debarkation. I glanced at the list when she had to sign it and it seemed like the items they had confiscated were steamers, irons, coffee pots, and
fishing poles. So those are definitely no-no's (and on the list of things not to bring). A six pack size soft size cooler is fine, just the rolling ones aren't allowed.