Which option; cx bike or mtb and road bike? I've done my research and i've narrowed it down to 2 options for me

Option 1: buy a low-end cyclocross bike for $1200
or 
Option 2: buy a low-end road bike for $800 and a low-end mountain bike for $400

My budget is $1200
I want a bike that will allow to me ride on the road and on the rough trails.
Please don't suggest a touring or hybrid bike because i don't want the relaxed geometry. I want to go fast. 
I'll be using these bikes for fitness and fun, not for commuting. 
So which option would be better for me?
Would a low-end road bike be better on the road than the low-end cyclocross? 
And would a low-end mountain bike be better on the trails than the low-end cyclocross bike?

Thank you for your input
I want a bike that will allow to me ride on the road and on the rough trails


I guess we can't be sure what you mean by "rough trails", but if you're talking about what I call "rough trails", a CX bike just isn't going to do it.


  i don't want the relaxed geometry. I want to go fast.


Relaxed geometry and high speed often go together off-road (think DH bikes).

On the road, a $1200 CX is not going to be as good as a $800 roadie, but that's only because of the knobby tires.

I think your best option is the road-mountain combo.

If you wanted one bike to do both jobs, I think a mountain bike with ~1.75" semi-slicks would be better than a CX. Plus, that won't cost you $1200.

A side note: No matter what you end up getting, you should buy used. You'll get much more bike for your money.