It's scale, specifically cottony cushion scale, Icerya purchasi. These are sucking insects and can be damaging in large populations. At this stage and if the rose not huge, picking or brushing them off is the most efficient way of dealing with them.

thanks, I did remove all of them , the tree is indeed pretty small, and I wiped each leaf with alcohol wipe, after that I sprayed with a hose, do you think that it's okay ? Also wonder if they would affect the roots, or do they stay only in surface ?

Only on the surface - leaves, stems, canes. If you got them all off, that's great. And an alcohol wipe is even better. Just keep an eye on things. There could be eggs present that may still have time to hatch.