Abstract: A roof for a computer rack aisle is provided. The roof has a canopy that may be flexible and/or fire-resistant. The canopy has a retracted position an extended position. In the retracted position, the canopy may be wound around a spool. In the extended position the canopy may cover the top of an aisle between two computer racks. A selectively releasable retainer holds the canopy in the extended position while releasing the canopy to return to the retracted position when a predetermined condition is met. The canopy retractor is provided to return the canopy to a retracted position. The canopy having first and second lateral edges with flanges running from a position approximate a front portion of the canopy and to a position approximate a rear portion of the canopy. The flanges can be received within a canopy guide track to facilitate the smooth movement from the extend position to the retracted position.