Actually, Octane uses the Metal/Roughness workflow. Your metal map would be used in the Specular/Reflection node channel, and since Octane uses a Roughness parameter instead of Glossiness, the Roughness map works just fine in that channel obviously. If you use the Specular/Glossiness map workflow, then the Glossiness map would need to be inverted before using it in Octane, because it contains the opposite values of a roughness map. It all depends on how the render engine supports specular and/or reflection parameters. That's how you'd decide which workflow to use. Some real-time engines that support PBR can use all of these maps together, like Marmoset. Real-time game engines almost always support metalness and roughness map workflows, and Blender will support metal and roughness channels in the PBR node too. To avoid confusion if you redistribute your scenes or maps, you can always simply rename the metal map as specular/metal, and supply both a glossy and roughness maps in your scene files too.

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