Cut brussels sprouts into quarters. Line rimmed baking sheet with aluminum foil. Toss together brussels sprouts and oil until coated. Sprinkle generously with salt and pepper. Bake 15 to 20 minutes, until lightly browned.
Meanwhile, heat medium saucepan over medium-high heat; add chorizo. Cook 5 minutes or until crispy. Remove chorizo for later use, discard any fat.
To saucepan, add pineapple juice, apple cider vinegar, adobo sauce, and garlic. Bring to boil; reduce by about 3/4.
After brussels sprouts have baked 15 to 20 minutes, pour pineapple juice mixture over brussels sprouts; toss well to combine. Bake an additional 5 minutes. Add chorizo and dates; bake 5 more minutes. Season with salt and pepper, to taste.
Transfer mixture to 4 bowls. Sprinkle with hazelnuts.