Roasty from W-34/70 or % choc

I was comparing notes on a dark lager I've been brewing over a year now.
The first time I had 3.4% chocolate and W-34/70 yeast. My notes say very roasty.
Later, I had almost the same % (1.5% choc, 1.5% carafa 2) but it wasn't very roasty.
Last, I had 2.2% chocolate with wy2206, but it was a tad astringent and not roasty.

So does the W-34/70 (wy2124, wlp830) accentuate roasty flavors over wy2206 ?
Or is 3% the crossover point ?

I wouldn't think it was the yeast, but I could be wrong.

Yeast strains do help certain flavors stand out, as you noticed in the the first W-34/70 batch and the first WY2206. Not to say that the manufacturer of your chocolate malts or degrees of roasting may have changed (i.e. used Thomas Faucett Pale Chocolate in batch 1 and Thomas Faucett Dark Chocolate or Briess Chocolate in batch 3).

As for the second batch that has 1.5% Chocolate and 1.5% Carafa II, I bet it was the Carafa II that made it not seem as roasty since the Carafas are kilned to not give off roasty, astringent, or chocolate flavors.

Hope that helps.

The named malts were the same across the batches.
I agree with your thoughts on the carafa. I was trying to lower the roasted flavor,
but it seems to have dropped out. I'll have to try with a bit closer to 3% next time.