Answer
The concept of pouring rose-water over the grave is baseless. Nowadays, this has become a custom and is considered necessary. Thus it is a Bid’ah (innovation) and must be avoided. Rasulullah (Salla Allahu Alayhi wa sallam) said, Whoever innovates something in Deen is rejected. (Mishkaat)
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai