Just tested if roofbags are affected in-game with the 7616.exe (the one with the bugged handgrenade code).

Turns out they aren't. Same is true btw for rooftop ventilation.

If the roofs get destroyed, sandbags and the roofvents keep floating in midair.

Good map to test this is D2 SAM site, as that map contains both roofbags and ventilators.