A single unit roof/rafters/insulation/ceiling will not benefit from ridge vents.
A "suspended ceiling" arrangement with the ceiling, then the insulation, then an empty space and then the roofing can use a ridge vent provided that the empty space goes all the way down to the eaves where there are soffit vents. This is rare unless you have a real suspended ceiling because a space of less than 18 inches between ceiling and roof will likely be completely filled with insulation.
When cleaning anything including baby diapers, it is better to sweep off or scrape off as much solid and semisolid material as you can first. (1) Less cleaning fluid or detergent needs to be used, (2) Less of a mushy mess which in turn means that bleaches or disinfectants will be more effective.