Added to Homebrews.
I'd rather find something a bit more exciting than Epic Will for the additional feat. If it's not another epic feat, we can simply swap Epic Will for Iron Will, though.
The Great Roc's statblock doesn't have an Epic Feat line for the Dire Charge, it is just stuck in with the standard feats.
It is actually standard to list the epic feats among the normal feats, post-Epic Level Handbook. I prefer that method myself, as it cuts out a(n unnecessary) line.
The two-headed variety looks to be a smarter version of the standard variety, with an extra bite attack. I strongly suggest that we drop the second boulder attack for these things, as that will boost their damage far outside their relative power level. Besides, just because it has an extra head doesn't necessitate doubling all potential attacks.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.