What are is the general rules regarding the mighty Roc Warriors and building hex's , can they capture buildings?

Roc Warriors can occupy the same hex as a building hex, but Roc Warriors do not gain the benefit of terrain tiles, so they will not get to ignore a damage when being attacked.

However, I'm not exactly sure what you mean by "capture." If a scenario requires you to occupy a building hex for some effect, the Roc can still do that. The Rules Reference says, "Though flying units are unaffected by terrain effects, they still occupy hexes. As such, they gain victory points for occupying hexes that contain banner markers." Maybe that helps?

You've answered my question , cheers.

I played a custom scenario called capture and control and it required you to occupy 2 buildings plus a victory point and I wasn't sure if flying units could occupy the building or as I put it capture the building. Hope that makes sense.

Once again thanks for the reply.