I’ve got S-04, S-05 and a smackpack of WY1272… which yeast should I use?
I typically use WLP001. You could use Pacman yeast and make a Rogue clone.
I’d use US-05 to let all the flavors you put in there come through without interference from the yeast.
I wonder if having some esters from the S-04 or 1272 might improve the perception of chocolate. I’m just guessing though.
S-04 would work well. It is not as estery as most liquid English yeasts, and it doesn’t ferment as dry as S-05 so it might leave a little more residual sweetness and body which is appropriate IMHO for the style. Sometimes I think that S-05 could ferment wood. 
S-04 would be my choice. 64F wort temp seems to work well. I’ve had it poop out below that on a couple occasions so 64F is as low as I go with it now.
I use 04 in all my Stouts / Porters. I ferment it in the low 60’s, ambient.
One more vote for S-04. A friend of mine used my milk stout recipe as a base for a chocolate stout fermenting with s-04. It turned out excellent! Very rich and chocolaty.
I usually use s04 but this time I decided to be different and went with the s05. Redbeerman is right, I think s05 would ferment wood. I think I wasted a lot of chocolate malt with s05. Its more like an American Stout but too dry imo. I’ve never been a big fan of roasted malts so I cut the roasted portion back but it still overpowers the other malts. Its conditioning more in the keg but I don’t have high hopes that it will taste the way I like.
I’m going to recommend Wyeast’s Thames Valley II for a chocolate stout with the caveat that I’ve never tried that yeast in a chocolate stout. I have, however, used it in a RIS and the smell of the chocolatey dark malts/grains and the esters from the yeast smelled about what I imagine heaven to smell like. It was sensational. So judging from that it’s worth trying, and I’ll definitely be doing it soon.
shoulda used 1450 ;).
I think this yeast does its best work in stouts and porters. And its pretty neutral to let the other ingredients shine.
Now that you mention it, I think I will try it. :) I’m kinda dark beer’d out for the time being though so it will be a little while.