Preheat the oven according to ham package directions or 375˚F.
In a small saucepan, combine the root beer, cinnamon stick and ginger and cook over high heat until liquid is reduced by half, about 10 minutes. Lower the heat and stir in the molasses and brown sugar, then cook a few minutes more until thick and syrupy (lower the heat if the glaze begins to bubble aggressively). Season with salt.
Set the ham on a rack placed over a rimmed baking sheet and brush the glaze onto the ham.
Bake ham for about 1 ½ hours or until heated through (about 10 minutes per pound), glazing the ham every 15 to 20 minutes. If the ham starts to brown too quickly, loosely cover it with aluminum foil.