The trouble with this system is that the roots which form are 'water' roots. They are very easily damaged when moving the cuttings from the water to potting compost. So, the length of your roots (their roots?) is about right for moving them on. They are still cuttings so they need treating for a while like that, keep them warm and moist as you would with a cutting done the traditional way. How long it takes depends on your growing regime, but at this time of year, they are going to grow quite slowly.

I don't usually use the water method because although mamy plants will root this way there is then the second shock of moving the rooted cutting into compost and losses can be high at that point

. I prefer to stick to the "cutting straight into compost method"

I don't even put my cuttings in compost, all mine are done in pure sharp sand in the cuttings frame.

I find 25% sharp sand and 75% potting compost is very effective.

I quarter fill a pot with seed compost the fill it up with sharp sand. The cuttings go in the sand and as the roots grow they find some nutrient down below.