Adama isn't arresting Roslin because he wants to seize power and have control over the entire fleet. He's arresting her because he believes that she has violated the agreement they made in the miniseries

ITA. I also think he's acting from anger at her persuading Kara against him too, but I don't think it's for power.

From what I remember *RM* says he's staging a military coup too. He uses those words to describe what Adama does.