In a small bowl combine 1/4 cup of the orange juice, 2 Tbs. garlic, 1 Tbs. tomato paste, and the sage. Place the meat in the slow cooker. Coat the meat with the mixture then sprinkle evenly on all sides with salt and pepper.
Meanwhile, heat the olive oil in a 10-inch, heavy sauté pan over medium-high heat. Add the onions, celery, carrots, parsnips, and the remaining garlic and sauté, stirring occasionally, until the onions are very soft and the vegetables are starting to take on a hint of brown, about 10 minutes.
Stir in the remaining 1/4 cup of tomato paste and the flour, and cook until the flour is no longer visible, no more than 1 minute. Remove the pan from the heat and add the wine. Return the pan to the heat, and raise the heat to high. Stir until the sauce thickens, about 2 minutes. Add the tomatoes, the remaining 1/2 cup orange juice, the stock, honey, and rosemary, and boil for 5 minutes. Add the tomatoes and stir to combine.
Pour the sauce over the meat in the slow cooker, cover, and cook on low (about 300F) until fork-tender, about 8 hours (ideally, turn the meat over halfway through to cook it evenly). Remove and discard the rosemary, then use a large spoon or ladle to skim the fat off the surface of the sauce. Transfer the meat to a cutting board and cut off and discard the kitchen twine. Slice roast, place on a warmed platter, top with sauce.