I think that it will be traumatic for the rats, tbh. Years ago, I kept rats and then got a terrier - and then had a baby. We ended up with a 3-zone house, which was very hard work and the rats had a much more limited life than was good for them. I suspect that a hamster could be too dim to be all that worried by the presence of watchful cats, but rats certainly aren't and will be stressed.
I have rats and a cat. Rats are kept in a cage in the bathroom, door always shut so cat can't get in the room. Rats can safely play out of cage in the evening.
On the odd occasion where dd has left the door open then the cat will go in and try and torment the rats through the bars. There is no way I would keep any form of rodent unless I had a room where the door could be shut to keep the cat out.
rats arent accutally affaird of cats my black dumbo blackstar bit a cat on the nose because it came into our room.but if you get a kitten you can train them beacuse rats and cat do get along great.www.freewebs.com/wolfmagicrattery
Hmmmm.... we got 2 rats when our old cat was about 15. She ignored them
We now have a new kitten who attacks everything - feet, hands, toys, furniture. She seems horribly fascinated by the rats cage. They don't seem to care about her one bit but I am too nervous to let them get together. Poor things are confined to the cage most of the time now