I've seen SCA's flip roomettes across the hall from me numerous times, and even the same roomette 2 or 3 times on #421/422 as well as 27/28. A couple years ago when I had to change my reservations a week before departure, I changed rooms twice (called 'shorts') as I couldn't book a roomette in #422 LAX through to CHI. I let the SCA know what was happening and even vacated my rooms 5-10 minutes early to facilitate their flipping the rooms. I even got to sleep in a family room for the first time ever.
As indicated above, how squeaky clean a room is when flipped varies from SCA to SCA. At a minimum, bed linens are replaced (if slept in), towels and wash cloths replaced, and a couple of bottles of water are put into the room. In Viewliners, they sometimes restock soap and t-paper, if they're not flipping 3-4 rooms at the same stop. It comes down to how willing are passengers to facilitate their room being flipped before they get off and how many rooms need to be flipped.
Perhaps my biggest pet peeve with flipped rooms is if it is after 8PM, give or take, they will have the beds down and fully made up. In my opinion, that makes it quite difficult for boarding passengers to find places to store their luggage, especially in Viewliner roomettes, and makes it near impossible to get changed to go to bed...IF they actually want to go to bed that early! I've seen completely befuddled senior citizens arrive at their fully made down roomette and wonder what to do next too many times! I had that happen to me, once, as well. Fortunately, I know how to make up/down the beds, so I simply 'flopped' everything back up top and enjoyed being seated for several hours before 'flopping' it back down.