Depends on the cement type. some can take up to 1 day, some 10min.
roofing cement can be used during winter time but you want it to be soft for easy spreading so you might want to put some cement in a can and drop that can into a pot to surround it with hot water to keep it soft until you dab it over the nail heads-- for now you can use a 2 inch scraper to apply a gernerous amount on each nail head that is leaking and in the Springtime or Summertime you can go up there and take a more thorough approach.
Rubber cement can dry in 15 minutes if it is not a very thick coat. If it is a thick coat, it will take longer.
The temperature and humidity can affect how long it take cement to "cure" or dry.
2 to 4 days
You will need 3.7 cubic yards of cement.
This depends on the physical form of cement (a block, granules, powder), temperature, stirring, acetic acid concentration, etc.
That depends on the thickness of the cement, the strength of the cement, the age of it, Is it reinforced
It takes a while for the Elmer's rubber cement glue to completely dry. It is recommended that you allow it to cure for at least 12 hours.