The recommended thickness for OSB used for roofing is 5/8 inches. However, the thickness can range from 3/8 to 3/4 inches depending on the look you want for your roof. The minimum thickness for roof sheathing is 3/8 inches. The thickness of the roof sheathing depends on several factors, such as the span of roof joists, snow load for the area, and local building codes. It is important to note that the thickness of the roof sheathing should be appropriate for the spacing of the rafters or trusses. The recommended nail spacing for OSB is at least six inches on the edges and twelve inches in the middle. It is also important to ensure that the roof sheathing is installed perpendicular to the frame and with a minimum thickness of 19/32 inches.