Preheat the oven to 350°F. Season the roast with salt, pepper, and sage, and place on a rack in a shallow roasting pan. Roast for 1 to 1½ hours or until the internal temperature reaches 145°F (medium rare) and 155°F (medium). Tent with foil and let rest for 10 minutes before slicing.
Meanwhile, drain the raspberries, reserving the berries as well as any juices. If necessary, add enough water to the juices to make ¾ cup. In a medium saucepan, combine ½ cup of the raspberry juice with the sugar, vinegar and spices. Bring to a boil over high heat, reduce heat to medium-low and simmer, uncovered, for 10 minutes.
Blend the cornstarch with the remaining ¼ cup raspberry juice. Bring the sauce to a simmer over medium heat and whisk in the cornstarch mixture, stirring constantly. Bring to a boil and simmer for 1 minute or until thickened.
Stir in the thawed raspberries, lemon juice, butter and food coloring; keep warm.
To serve, slice the roast and arrange on a platter with raspberry sauce on the side.