Been there, done that. In my experience roof lights cast a LOT of light on your hood, even with a hood blackout. You can forget any driving/euro beam lights for the roof. The best would be pencil beam or fog.
It's just not worth the headache for me. For as often as I use my lights for wheeling at night having a bunch of lights on the roof didn't make sense. The two Hella 4000 100W cornering beams on my front bumper are more than adequate.
If you have a roof rack then I guess putting some fog or pencils up there wouldn't be bad. But I wouldn't buy a bar specifically for roof light, not worth it when bumper mounted lights will accomplish the same thing without the glare. Roof lights also suck in the snow because they illuminate everything right in front of your face making it hard to see. I plow snow in the winter and on my way into work at 2am in a snowstorm I'll usually run just parking lights because its actually easier to see.