I would leave it for now. It seems like your rose is pushing new growth so you don't want to take it away. It will get better growth and later you can remove it, but for now I wouldn't bother it and just let it grow. Congratulations on a successful rooting! It is outside right? I can't tell good from your picture? Maybe it's not getting enough sun? It needs morning sun or dappled shade to push strong growth.

Yes, the cuttings are outside. Until yesterday they were wrapped up (burrito method) and when I unwrapped them they all had good calluses plus this white growth. I've put them in a damp mixture of light potting mix and sand and left them in a protected position outside which is East facing. Hopefully, they won't all die!

Tuderte, if you have just unwrapped them, I would make sure that they are in a completely shaded area for a little while so that they can acclimatise. You might still loose that new growth though. Just my opinion.

Hope they set roots for you and grow into big beautiful rose bushes.

Sharlene