There is the possibility bearing in mind it's 2012 we're talking about that the other infamous doctor of the time, Leinders, would have been the one - Kohl attested to Schmidt being involved in his doping, and he was part of the Humanplasma circle. This then involved Michael Rasmussen, from whose testimonies we have a link to Leinders, and we know that oversight and assisting riders who were doping from returning positive tests was a large part of what his role at Rabobank was known for.This I posted before, but is worth remembering, this is not just about Rozman at Sky/Ineos -
There is, or was, another person involved who had direct contact with Schmidt at Sky (Laptop "specialist" Dr Freeman, or a rider?)
So this is not just about Rozman at Sky, and the potential one "bad apple" excuse aint gonna wash.
The other possibility if we are talking riders and race-side staffers would leave a couple of other relevant possibilities. Somebody who went from Milram (where Mark Schmidt had been prior to this) to Team Sky was Christian Knees, who was picked up off the scrap heap when Milram collapsed at the end of 2010 and repurposed into a rouleur domestique par excellence by the team, and was at the 2012 Tour. Sky couldn't really pick up any ex-Gerolsteiner riders with their farcical white paper strategy at the time (despite having the likes of Mick Rogers of course), but Milram were likely fair game as they'd been an underfunded, mismanaged mess over the time since the bottom fell out of German cycling in 2007 and Petacchi had had his ban, so their results had not been especially noteworthy and there wasn't so much suspicion of them at the time as there might have been 2-3 years previously. However, probably a more logical connection than somebody in a relatively peripheral domestique position as Knees was, would be Servais Knaven - he is a known doper with his own history, as has long since been known, and he had been at Milram as a rider in 2009-10 before joining Sky as a DS, where he stayed all the way until 2022, being one of the men in the car for several of their greatest successes.
This is all pure conjecture and theory-crafting, I hasten to add, but these would appear the line-of-best-fit avenues of discourse.