My Mom and Dad live together in retirement home but my mom's dementia is making me wonder if we should be looking at a different placement. How should I start looking?

Yes, the assisted living place should be considered for him, and the memory unit for your mother. If they are close together, he can visit often.
Many ALFs have memory units in them, so if you have one of them nearby, that is also an option - then he could visit within the building. This change will be hard on your dad, and your mom will notice the different apartment, but since she can't form new memories very well, she shouldn't notice the difference too much. It's good that your dad recognizes that he can't keep doing this. If he doesn't get relief, your mom may lose him all together. Please look at some changes.
Take care,
Carol

Kwriter, first of all YAY that your dad made the move already and saved you kids a bad headache and heartache with having to FORCE them to move. That in and of itself was a godsend. The asst living place that my mother-in-law lives in has a retirement section as well as the memory care unit nearby or attached so if and when we have to move her it'll be much easier. When we were looking for asst living for m-i-l one of the criteria for them in whether she could live just plain independent or asst living was, in case of an emergency would she be able to follow instructions when exiting the building? Our answer, probably not. Her memory is so bad she wouldn't have been able to remember what they said, plus with her macular degeneration she wouldn't been able to see well enough. They did have the option in the retirement section though to hire an aid to help the person who wasn't quite ready for the full asst living. They charged by the hour but it might have been an option for us. In your case, your dad sounds like he's got all his oars in the water and if he thinks it's time to move them, I say he ought to know. It won't matter to your mom since like you said she already thinks she's living in a new place anyway. Gotta keep him as healthy as possible at this point since he's in charge of her. But if he were to die suddenly it will be so much better to have her already in place for the help she's going to need. Kudos to your dad.

There was one place that offered both retirment and asst. within the same unit. But other family members who had experience with it, were really admant the place was not a good place to be at. The one he is in has the retirement center and asst. living and nursing home across a busy street. The memory unit is down the street a block. I think maybe he should try their day-care program, which is very reasonably priced. He isn't willing to do it though.

I mean retirement apts. are on one side of the street and asst. living on the other.