There’s a “ConvertFromDiffSpec” material function in engine content that allows you to do this. This converts classic Diffuse + Specular textures to BaseColor, Metallic and Specular. In your example the gloss map should be inverted (for example with a OneMinus node) and would go into roughness.
This adds a handful of instructions, but the impact is quite minor so it might be worth it to save you some work. Converting a bump to a normal map can technically also be done inside your material, but this is quite expensive, even at a low quality, so I would recommend converting those outside of unreal.