I voted for Technician.
Rockmon may be fast and all, but you need to remember that of all 9 or so priority moves, 4 hit this guy SE (mach punch, Vaccum Wave, bullet punch and aqua jet) and they are capable of hitting really hard. Considering how the common users of said moves are very powerful attackers (hi Scizor, Metagross, Machamp, Azumarill, Breloom, Lucario, etc) and somewhat bulky, you can be sure as hell that the Earth Power/Rock Move/sub/CM or whatever set will have a fairly considerable number of counter and/or checks. Add Special walls like Lax and Blissey, bulky waters, Revenankh and some other pokes and you will get a pretty big number of checks around. Now what is the point of this? well, if we want to have a sweeper, you will need to give it the ability to at least fight back against some of said checks and counters, and the best way to do it, IMO, is with the versatility of Hidden Power. Technician gives Hidden Power 90 BP, making it more powerful, which is why I am voting for it. Simple as that.
But that is me. I've always liked the idea of a special sweeper that could abuse technician and hidden power and my vote reflects that.
As for Ancient Power, I'd much rather discard it from the movepool if it is that much of a problem honestly. I mean, Lunatone is a "rock special sweeper" (well, uh, a very weak and slow one, but still) and it doesn't get Ancient Power. Absolutely nothing stops us from removing ancientpower from our technician rock special sweeper.
Rockmon may be fast and all, but you need to remember that of all 9 or so priority moves, 4 hit this guy SE (mach punch, Vaccum Wave, bullet punch and aqua jet) and they are capable of hitting really hard. Considering how the common users of said moves are very powerful attackers (hi Scizor, Metagross, Machamp, Azumarill, Breloom, Lucario, etc) and somewhat bulky, you can be sure as hell that the Earth Power/Rock Move/sub/CM or whatever set will have a fairly considerable number of counter and/or checks. Add Special walls like Lax and Blissey, bulky waters, Revenankh and some other pokes and you will get a pretty big number of checks around. Now what is the point of this? well, if we want to have a sweeper, you will need to give it the ability to at least fight back against some of said checks and counters, and the best way to do it, IMO, is with the versatility of Hidden Power. Technician gives Hidden Power 90 BP, making it more powerful, which is why I am voting for it. Simple as that.
But that is me. I've always liked the idea of a special sweeper that could abuse technician and hidden power and my vote reflects that.
As for Ancient Power, I'd much rather discard it from the movepool if it is that much of a problem honestly. I mean, Lunatone is a "rock special sweeper" (well, uh, a very weak and slow one, but still) and it doesn't get Ancient Power. Absolutely nothing stops us from removing ancientpower from our technician rock special sweeper.