Redundant vent in roof

Was poking around the attic yesterday and noticed (for the first time) an awfully cold draught coming in from outside.

There are three runs of brown piping (one for extractor fan in each bathroom), which have their own vent 'hole' in the roof. Kinda hard to describe in text, but the brown (almost like sewerage piping) runs to the roof and is then vented out through raised vent covers in the slates outside.

However, it seems to be that one too many of these vent holes has been cut into the roof, and therefore I effectively have a 'hole' in the roof. Any suggestions of how best to rectify — expanding foam or something like that??

I would not be too bothered.

It is normal for a roof space to be well ventilated - this helps to stop roof timbers from rotting.

Sorry, maybe I should have specified. There was a strong, cold draught (that's making me thirsty) through the house which is why I went investigating. I'd say this is the source of it.