"Rooled up holiday pay" means paying
one or more employees an amount for holiday pay which is included in the
hourly rate, rather than being paid when the employee actually takes
Because the law is not clear on when this method of payment can or cannot be used, the SIA will be considering each case on its own merits before deciding whether or not the employer should be using the technique for your holiday pay.
You can find more information on this on this SIA update newsletter