I have Asphalt Roads installed, and the resulting recipe is not so good, it was not good in the first place, crude oil, fuel oil, and stone bricks... eh. I would like to see something more real world? I thought about simply adding an asphalt item and making it part of the Crude Oil Fractionation output. But then it would be a constant production item, probably better to have a specific recipe for production on an as needed basis. Thought I might post the thought here to see if you had thoughts or plans.

Also, it seems that if one does not have the Carbon mod installed... there is no use for carbon?

Not sure if possible (nor the amount of effort required), but have you considered using a boiler and the graphics from the Manifolds mod to make a fractionator? I think it would have the functional idea with more appealing pipe fitting?

I thought about simply adding an asphalt item and making it part of the Crude Oil Fractionation output

I'd probably make it use bitumen or add a new recipe to make it from bitumen. Cause that's essentially all it is https://en.wikipedia.org/wiki/Asphalt

Also, it seems that if one does not have the Carbon mod installed... there is no use for carbon?

You can burn it, including in a gasifier to get syngas. It's intended that there's no direct use for it.