For mashed rutabaga, combine 1 cup diced rutabaga and cold water to cover by 1 inch in a medium sauce pan. Bring to a boil, and reduce to a simmer; cook until tender, 30 to 45 minutes. Drain and let stand until dry. Transfer rutabaga to the work bowl of a food processor and pulse until smooth, scraping down sides, if needed. Let mashed rutabaga cool completely before using in rolls.