I've cruised w/a rollator/walker several times; sometimes it's mine, sometimes rented. I leave in 3 weeks w/mine for a TA.
I take the rollator especially for tender ports. I usually cruise w/Princess & the rollator is allowed (folded) on the tenders. The roads on shore are often bumpy, but I can managed for short distances. Rollators are really handy to carry things too.
Also, I've never been refused taking it on a tour bus (in the luggage hold) on a ship-sponsored excursion. I'm booked on a private excursion next month in Iceland. I did tell the company that I would have a rollator w/me. I shall remind/reconfirm w/them in an email next week.
For general use on the ship, I rent an electric scooter. A 900-ft. long ship is too much walking for me, hence the scooter. Each of my vehicles has a purpose.
And always ask the excursion staff on your ship -- what's possible or not.
