They appear to have caught him red handed with his laptop open and logged into SR at the San Francisco Library. Sure it would be possible that he was just a moderator that was hired after it opened, but this would not explain how his email address was used for the forum account that posted the first advertisement about silk road (I think it was a weed/drug related forum).
Yeah they got him with his laptop decrypted.
My main concern is that it clearly doesn't PROVE it's him. Just because he was "allegedly" the first person to post a link to the SR (he didn't even advertise it, just said he was thinking of placing an order there) doesn't mean he owns it and the proof that it was him who posted it wasn't so straight forward either. It definitely makes him a suspect, but it definitely doesn't prove he's DPR IMO. Combining it with all the other circumstantial evidence doesn't really prove anything either. I have yet to see any hard evidence tying him to that identity.
Who's to say that circumstantial evidence wasn't planted by the real boss of SR to cover his tracks.
You should remember that the FBI apparently was able to seize several thousand bitcoin when they got his laptop (although this also may have been the result of seizing the servers in iceland).
30k came from a SR server, 140k came from his laptop. By the way, it's interesting to compare these figures to the estimated volume of the SR mixer.... I have a feeling they didn't find all the BTC, the numbers seemed way off when I looked at it. If I was running a website like SR I sure as hell would have a ton of cash tidied away safely, perhaps a paper wallet or such....
Ross' excuse for the 140k on his laptop was that he was an early adopter and high-frequency bitcoin trader and he earned those Bitcoins from that. This is what his friends and family thought he did for a living too. I haven't seen the FBI come out and say "these coins came from the SR mixer" or prove in anyway they were involved in the SR. It's a plausible excuse, I wish the FBI would investigate this side of the case more but they probably won't seeing as they'll likely win that asset forfeiture so why would they care.