The 18-year-old spent part of the season on loan at Ilkeston Town.
Millers' chief operating officer Paul Douglas said: "David has agreed terms on a one-year contract and we are delighted to have him for another year.
"The club has an excellent record of producing homegrown talent with the likes of Ryan Taylor, Stephen Brogan and Jamie Green all becoming first-team regulars and we have similar hopes for David.
"He has a lot of hard work ahead of him, but he has the potential to become a very good player for this football club."
Haggerty's only first-team appearance was as a late substitute in the Millers' final game at Millmoor against Barnet in May 2008.