I don’t know what you mean by “rolling your positions” but I don’t think there is such thing.
There is no rolling of positions. Your annual ISA allowance is significant for one and only one purpose. “The amount of money you can inject during that tax year”
Lets say you have managed to deposit £12000 from 6 April 2020 to 5 April 2021 into your ISA. It does not matter what the “value” of this 12K investment after that point, it can be 10K or it can be 100K any appreciation made by what ever you earn is tax free. Also you can sell and buy anything anytime “inside the ISA wrapper”
In fact when you try to deposit money into your ISA on or after April 6th 2021, you will see a warning/aggrement on your ISA provider (Trading 212 or others) telling you that it is a new tax year and you are contributing for a new year.