Spray 3 1/2- or 4-quart slow cooker with cooking spray. Add broth, brown sugar, soy sauce, chili garlic sauce and gingerroot to slow cooker; stir with whisk to combine. Stir in green onion whites. Reserve green onion greens for garnishing; cover and refrigerate until ready to use. Add roast to slow cooker; turn to coat. Cover; cook on Low heat setting 8 to 9 hours or until very tender.