How does the author use foreshadowing in Wolves of the Calla?

In this novel, Roland and his ka-tet, Eddie, Susannah, and Jake, are following the Path of the Beam in their quest to find the Dark Tower when they are met by a group of people from a nearby community called Calla Bryn Sturgis. These people have been plagued by what they call Wolves for many generations. The Wolves come to their community and steal one child from every set of twins born in the community, only to return them weeks later with brain damage and a tendency to grow to giant size. This foreshadows Roland and his Katet eventually fighting these wolves.