Does plywood need to be placed under the 10 ft. Corrugated Galvanized Steel Utility-Gauge Roof Panel if using it for a roof?

Gibraltar corrugated panels are intended to be installed on solid decking.

Corrugated roofing panels have a double overlap side lap, which means the 25-5/8 inch panel only yields 21-1/2 inch coverage. Gibraltar corrugated panels are intended to be installed on solid decking that is at least 15/32 in. plywood or 7/16 in. OSB. As always, check your local building codes regarding framing and substrates.