Question
Few hours ago, my rose plant was full of leaves, now it is portion of the leaves left as if it has been sliced off. Certain branches has snapped off. What could be the reason for this? Is it natural for this to happen? I live on the second floor, no other access to the plant besides me.

Answer
The only thing I can think of is mice and birds. I know that Crows damage roses in my garden. Sliced off means something has eaten it and it has to be fairly large as rose insects take time and small bites. Beetles would be the most voracious and take the shortest time to devour a rose.