"Rota" is perhaps "Roster" in your part of the world.

Why complicate things?
Use old fashioned paper and pencil and draught out your ideas, draw bubble diagrams..etc and then see if you can see where I am coming from.

With respect, now I see your problem, I have dealt with this type of problem for some 40years, long before Excel was invented, unless of course you have an early prototype called "Excelsious" used by the Roman Empire.