On your place I would split BSDFs for diff colour / texture and for Gloss / roughness.
So that you'll have bright colour (like any rubber based material) and diffused gloss ... plus variation on roughness map would do.
I wouldn't go crazy with the bump / normal map (apart from custom details - i.e. logo, pattern, etc) since the rubber itself is pretty uniform - maybe some micro bump (also depends on your shot)
Introducing rough thin film (Tom's concept) is pretty nice touch - basically for any dielectric material.