For Raspbian OS I know that the bootloader partition needs to be increased in order for it to work on an rpi4. For the unfamiliar, this can be tricky and easily lead to unbootable systems.
Let’s see what @spockfish has to say for RoPieee specifically. Might not be worth the trouble though. Reflashing is quite easy
Be aware that the RPi3 and RPi4 boards are physically different. I did this recently and had to buy new cases to accommodate the differences in the physical layout. I reflashed by the way.