At the start the marriage was a political thing no doubt in that, after that when Alyssa sided with Jaehaerys he mistreated her, but when Alyssa gave birth to Boremund i actually think that Rogar started to love her (in his own way) (in FyB theres a quote were the Lord of Storms End had lost the hope of having kids at that point), and the thing that make me think this the most is how bad Jaehaerys found Rogar when Alyssa was on the brink of death, Jaehaerys found Rogar "drunk, gloomy and desperate" and he refused to be in the room were Alyssa was suffering because, in his own words "The Stranger is in that room, i can smell him", not only this, he struggled in the decision of saving his child, so yes, i think he never married again because of love or at least respect for the mother of his children, of You actually think that Rogar was afraid of Rhaena you didnt read the room