Preheat oven to 400° F. Toss yams with salt, pepper and about 1 tablespoon oil to coat; roast until browned and soft throughout, about 15 to 25 minutes. Cool in refrigerator. To caramelize onions, heat 2 tablespoons olive oil over medium-high heat until hot, add sliced onions and let sauté for about 3 minutes without stirring. Continue to sauté over medium-high heat, stirring occasionally until onions begin to brown. Reduce heat to medium-low and continue to slowly sauté, stirring about once a minute until the onions are soft and brown. This process can take 15 to 45 minutes depending on desired darkness of onions. Cool in refrigerator. Oil kale with remaining olive oil (about 1 tablespoon). Roast in oven at 450 degrees for 3 minutes, or until soft but not browned. Let cool fully in the refrigerator. In a food processor, combine roasted garlic, thyme and red wine vinegar until dressing is blended. Combine all cooled ingredients with dressing and toss to coat.