I forgot to boil the milk before I added rose milk essence in it. Could I boil now? I have been keeping the mix in the refrigerator for 5 hours now. I am not sure could I boil the milk now or not.
I assume you are talking about using raw (unpasteurized) milk; and want to make it safe for drinking.
I think you can boil it with the rose essence in it. It should not make a difference either way.
At worse it will taste cooked.
This link will show two ways to pasteurize the milk, either at low or high temperature.