Rather than print to buf and then copy to pointer->data, skip the middle-man

 while(fgets(pointer->data, sizeof pointer->data, f) != NULL) 

Rather than start count at 1, start at 0 and skip the final decrement.

 int size = 0;
 while (...) {
   ...
   size++;
 }
 // size--;

Simplify malloc() usage, IMO this style easier to maintain and less error prone.

 // root = malloc(sizeof(struct node));
 // pointer->next = malloc(sizeof(struct node));
 root = malloc(sizeof *root);
 pointer->next = malloc(sizeof *(pointer->next));

Like the setting the pointer to NULL after free(). A good compiler will optimize out if it can, but good to scrub pointers when done.

 free(pointer);
 pointer = NULL; 

Rather than print to buf and then copy to pointer->data, skip the middle-man

 while(fgets(pointer->data, sizeof pointer->data, f) != NULL) 

Rather than start count at 1, start at 0 and skip the final decrement.

 int size = 0;
 while (...) {
   ...
   size++;
 }
 // size--;

Simplify malloc() usage, IMO this style easier to maintain and less error prone.

 // root = malloc(sizeof(struct node));
 // pointer->next = malloc(sizeof(struct node));
 root = malloc(sizeof *root);
 pointer->next = malloc(sizeof *(pointer->next));

IMO, initializing the complete structure promptly after memory allocation is a good thing. (Also with root)

 pointer->next = malloc(sizeof *(pointer->next));
 pointer = pointer->next;
 pointer->next = NULL;
 pointer->data[0] = '\0';
 pointer->other_fields = 0;

 // or

 pointer->next = calloc(1, sizeof *(pointer->next));

Checking if malloc() returned NULL is good also.

Like the setting the pointer to NULL after free(). A good compiler will optimize out if it can, but good to scrub pointers when done.

 free(pointer);
 pointer = NULL;