I read the books first, but as the books went on, it was easier to see Gabaldon's heavy hand in how she painted the "obstacles" to Jamie and Claire. Her writing makes it so that Jamie has to be coerced or cajoled into sex with anyone besides Claire. When he marries another woman, it's under pressure from his sister and false pretenses (he never would have married Laoghaire if he'd known her full role in the trial). Frank seemingly cheats with a string of (younger) women and is a racist, too! A lot of white people born circa 1902* were, granted, but it seemed more like Diana wanted Frank to be really unlikable right before he died, all the better to make Claire more sympathetic and justified for spending years emotionally checked out of a marriage she chose to continue.
I think Frank's plan with the gravestone is beyond convoluted but withholding the knowledge that Jamie survived Culloden? The wrong choice but one many men in his shoes would make, if he thought she'd leave forever and take the child with her. The story would be boring if everyone did the right thing.
Book Roger reminded me in some ways of "Meathead" from All in the Family: a progressive with some chauvinistic tendencies. The modern book characters generally acted like people born in 1918 or the 1940s, even if they did unconventional things sometimes, while the show wants to smooth them out so they're "relatable" to contemporary viewers. That approach runs into problems when the story says Roger has lingering hangups about Bree being raped, or the modern characters interact with enslaved people and slaveholders without personally doing much to eradicate the institution on a societal level. That would not have been an expectation from a 1990s romantic sci-fi/fantasy novel but the show is being made in a different time. I wonder if people who see the show first go into the books expecting the characters to be more enlightened and are disappointed when that's not the case.
*The books allude to a sizable age difference between Frank and Claire, and they married when she was 18. The show completely omitted this dynamic, or any sign that Claire/Frank might have been wrong for each other, even without the time travel.