Well, you could buy a Gold Wing (2006 and up) and have a toe warmer vent to help you out.
But since we are talking Rockets, heated socks (check Gerbing or others) would be a good bet, I also got some foot warmer packets (haven't used them yet, but my son does when he goes on his winter camping trips...like last week) that I will probably use when I get to my new camp in a couple of days.
I'm not sure if Gerbing offers them but if they do I would recommend a sock with the battery in the top of the sock if they make such an animal. The reason being is that if you have to "hook" it up to your bikes electrical system it seems like it would be a pain to attach the wires to the socks, your gloves, your jacket...etc...
I ended up buying Gerbing "Core Heated" gloves with the 7 volt battery in the top of the glove for use over here to see how well they work, again I didn't want to have to deal with the wiring and such. I also bought an extra set of batteries so that the gloves can still be used while the other ones are recharging.
I know you didn't really ask about the gloves but I figured that if they offer gloves with battery packs...maybe they offer socks as well. If the foot warmer packets work (for any lenght of time) they would probably be the most cost efficient way to go.
Dennis