What kind of rooms? Need more info please so you can get appropriate suggestions/solutions.
You can decide a room with some simple furniture arrangement, folding screens, draperies, bookcases, etc.
These ideas might help: https://www.diyncrafts.com/37609/decor/30-imaginative-diy-room-dividers-that-help-you-maximize-your-space
This one is cute! https://www.hometalk.com/12563559/twinkle-lights-room-divider-makeover
And here's one that isn't as flashy, it uses doors https://www.hometalk.com/7842796/diy-room-divider
Old picture frames