To determine the most suitable roof type for covering spans greater than 9 meters, it's essential to understand the common roof types used in construction and their span capabilities.

1. Aisle Roof: An aisle roof is typically used in buildings with additional supporting structures like columns and is not specifically designed for long spans unsupported. Thus, it is not ideal for spans greater than 9 meters.
2. King Post Truss: This truss is suited for short to moderate spans, usually up to about 8 meters. It is a simple truss that becomes inefficient economically and structurally when the span increases above this range.
3. Queen Post Truss: Queen post trusses can efficiently cover spans up to 10-14 meters due to their design, which involves two vertical supports (queen posts) and can withstand longer spans than the king post truss. This makes the queen post truss the most suitable option for spans greater than 9 meters.
4. Couple Roof: This is a simple, straightforward structure ideal for smaller spans, typically 4-5 meters. It's not intended for spans greater than 9 meters.

Hence, the Queen post truss is the best choice for spans greater than 9 meters, as it provides the necessary structural support and economic efficiency.

Conclusion: The most suitable roof type for covering spans greater than 9 meters is the Queen post truss. This decision is based on its capacity to manage longer spans efficiently with adequate support structures.