If the Yes-voters were paying attention to the fight with Durkula, they'd know Roy can lay down some serious smack, even against spell casters. They probably don't know that it's an undead-bane enhanced effect, so they won't want to risk a fight with him.
Protection from Daylight is not a standard D&D spell; it's homebrew. So we don't know how long it lasts. However, a reasonable guess is that it lasts 1 hour/level. If so, it depends how it was cast. If from the staff, then most likely the level applied would be Malack's, which was level 12. If Durkula learned the spell (which I'm fairly sure he has), it could be with his caster level, which is 14 or 15. In either case, it will last until long after sunset.
BTW, there's only one vampire out front, or at least we've only seen one.