Is it good ideat to compress diffuse and roughness texture to one RGBA texture?

Is it good ideat to compress diffuse and roughness texture to one RGBA texture?

I’am going to make many models that will be using only diffuse and roughness textures, and I wondered if it is posible to compress them to one RGBA texture where RGB is diffuse and A is roughness.
Is it good idea?
How to set up something like this in UE?
What image encoding to use?

Yes, it is good idea. You do not need any extra setup. Pack them into any image editor and import into UE.

Indeed, similarly how RMA uses for texture budget. I usually use compressed textures for my all-level assets.