... Well, having not actually PLAYED 358, but having heard that Mickey appears just for one scene, I wager that could be a reason Mickey never showed up much in that game: if he saw Roxas, his reaction would be a pretty dead giveaway to whether he remembers Ventus or not.

See, we have no idea if they met during 358, but during KH2 the only way they could have interacted was if they met somewhere in Twilight Town, which I think is not possible. Mickey arrived there from Yen Sid's tower, I presume... you know, what WAS Mickey doing in Twilight Town? I can't recall if they ever stated WHY he was heading there: did Yen or Riku tell him that was where Sora would wake up? I may be confusing manga and game canon now, but to my memory didn't Riku and Mickey meet up in Twilight Town when he first got off that train?

And to return to the point: no, I don't think Roxas and Mickey ever did meet one another in KH 2. By the time Mickey gets into the town, Roxas is already within Mickey.