At the time that Tigh was dealing with Roslyn, he had about 50 things going at one time. It wasn't until things had settled down, and people had some time to think that Adama and Roslyn had their little discussion.
If you recall correctly, it was Adama, and not Tigh who threw Roslyn in the brig. Tigh was merely tasked to carry out the order. In retrospect, i'd have to say that Tigh's decision to impose martial law was probably a good one. He didn't need the hassle of the civillian government at the time. Things were pretty chaotic. Admittedly, taking his wife's advice about sending in the Marines was not a good one. His original plan to sit down with the various ship's Captains and explaining the situation was probably a much better alternative.
Lee Adama is going to bite it...mark my words..hes become a wuss