Under one roof Definition 1 of 2Pro Tip 1/3Inclusiveness Used to express a gathering of different items or people in one place. This marketplace offers products from around the globe under one roof. Pro Tip 2/3Convenience Implies the benefit of having everything accessible in one location. Our new office has a gym, cafe, and daycare under one roof. Pro Tip 3/3Event Organization Often used for events where people or items are brought together purposefully. The trade fair will take place under one roof at the convention center.