How to fix chimney hole in roof?
This should really be fixed from the outside first and an appropriate water barrier placed over the hole. If your only concern is closing the hole you could simply cut out a piece of plywood (mashed wood) to fit the whole and then use one or two small strips of wood to screw that piece into the surrounding wood. Something similar to the below:



Then fill the cracks with a foam. However, all this would do is seal the hole from any real air flow, but would leave a potential problem for leaks if any water was to get under the tiles. As such it is really recommended to get who ever fixed the tiles to come back and do things properly.