Jamie being a man of his time, for me, accounts for why he beat up Roger before trying to confirm who Roger was or why he was there, or telling him who he was.
But as for the rest, I'd argue that the problems of this episode were mostly as a result of people not sharing information with each other, all the way back to Brianna not telling Lizzie that she was leaving the tavern with someone she knew and trusted...her friend Roger, back when she first took off with him in Wilmington. (I still can't wrap my head around that. Yes, yes I know she was excited to see Roger, and probably not thinking clearly. But Brianna and Lizzie had just traveled across the ocean together, Bree knows how dangerous the 1700's can be (between her own experiences and stories Claire told her) and they were basically alone in this place neither of them knew, where neither of them personally knew a soul. Whether or not Bree felt OK leaving with Roger, you'd think for a second she might say "oh, wait, I've just left a woman alone in a tavern, an ocean away from her home, and I'm the only person she knows here. We've had each other's backs for weeks, and technically, she's charged with, responsible for, looking after me...hmm maybe it might be kind to mention to her that I won't be back for a while so she doesn't worry/go wandering around looking for me, putting herself at risk")
So Brianna not telling Lizzie she'd run into her on again, off again boyfriend, now hand-fast husband, and not sharing she'd had wildly different encounters with two men that day (that part's understandable given her trauma)l Brianna not telling anyone for months about Stephen Bonnet; Claire not telling Jamie about Bonnet; Jamie, Ian, Lizzie not mentioning to Claire or Brianna that they'd seen the man from Wilmington at Fraser's Ridge - before taking action, and then not mentioning it soon after they'd gotten rid of Roger, when it would have been more feasible that they could go get him without traveling months, Jamie not correcting Claire's assumption that he'd hurt his hand on a tree ... lack of sharing information made things worse. It was just bad communication.
Maybe Claire and Jamie's "we can have secrets, but never lies" promise needs to be updated now that their in the new world?
On a different subject, I'm guessing that Roger is not going through the stones, partially because he won't decide to leave Brianna (for all he knows, there are violent maniacs roaming around near Fraser's Ridge, randomly and brutally attacking strangers and selling them into slavery, he'd want to find Bree and make sure she's safe) But also, I can't imagine that Roger, being exhausted, injured, disoriented, unfamiliar with the territory or landscape, not used to traveling unnoticed in the woods, would be able to completely evade a group of non-exhausted, highly motivated Mohawk searching for him on foot and horseback, even if they are out of their home territory. It will probably be like Claire trying to go back to Frank through the stones....just as she's standing there, someone comes up and captures her, dragging her away.