Who is the narrator, can she or he read minds, and, more importantly, can we trust her or him?
Third Person (Limited Omniscient)/ First Person (Peripheral Narrator)
In narrative terms, Roots is the equivalent of an M. Night Shyamalan film. Author Alex Haley tricks us into thinking one thing throughout the entire story…only to shake things up with a twist in the final moments.
For most of the time, we think we're dealing with standard third person, limited omniscient narrator. We spend our time in the heads of a series of main characters—Kunta, Kizzy, Chicken George, and Tom—and occasionally take a dip into a minor character's perspective for a paragraph or two. Nothing to see here, folks—move along.
But then our genealogical study hits Alex Haley: our narrator. From there, we shift to a first person perspective as Haley discusses the oral tradition behind the story we just read, his research into its validity and finally its confirmation. This has an interesting effect: it both reveals that the story we just read was written by its main characters' ancestor (dang) and validates it as a legit historical document.
Of course, there's much debate over the historicity of Haley's genealogical claims, but that doesn't really matter when thinking about Roots on a literary level. In this context, the reveal that Alex Haley, Kunta's distant descendant, is telling the family story, just further emphasizes Roots' focus on family lineage.