I went into Rogue Trader practically on the back of finishing Pathfinder: Wrath of the Righteous, and a few years after having played Kingmaker, so I knew more or less what to expect from an Owlcat game. In most aspects it did indeed turn out to be very comparable to their other titles, but in other ways it was clearly a departure. I will mostly try to approach this review from that perspective, although hopefully the main points should be clear even if you have not played the previous titles from this developer.
The most obvious difference is, of course, the setting. I have never particularly been a fan of 40K, it has always seemed particularly and deliberately unsuited to telling a nuanced story at a human level, so I was initially apprehensive at the idea of an entire CRPG 'shackled' to this silly, over-the-top, grimdark universe. Throughout the game, you do get the impression that there is tension between the lore and tropes of the setting on one hand, and the desire to tell an intricate story with compelling characters on the other hand. Fortunately, Owlcat does an admirable job of walking this tightrope. There is plenty to lap up for 40K fans; basically every aspect of the setting is explored and the party roster is a who's who of all the various archetypes they're likely to be familiar with, and I suspect Games Workshop had them on a tight leash in this regard (I am still miffed that you can't romance Argenta).
At the same time, despite these severe restrictions, they still managed to tell an intriguing story where you gradually become invested in the fate of your dynasty and your party members. In that sense, it reminded me of that other Warhammer (Fantasy) release, Vermintide 2, although it is obviously a very different style of game otherwise. The characters and descriptions occasionally fall into the trap of being overly verbose, but overall I am a fan of Owlcat's writing, and Rogue Trader certainly did not change my opinion on that.
Mechanically and in terms of gameplay, unless I'm mistaken, it seems that the game is based on a homebrew version of the tabletop game of the same name. That means it is basically uncharted territory for a video game, and you do get that impression from the fact that it is constantly being tweaked through patches and hotfixes. In typical Owlcat fashion, there is an absolute plethora of talents and abilities to choose from, with various possible archetype combinations, and choosing what to pick can be overwhelming during your first playthrough, especially at the start.
What notably sets Rogue Trader apart from Wrath of the Righteous is that it is quite easy on the standard difficulty, provided you are a CRPG veteran and/or willing to master the mechanics. You can quickly output absurd amounts of damage if you know what you're doing and are able to effectively (ab)use the action economy, especially with certain OP characters such as Cassia. For experienced CRPG players I would recommend that they increase the difficulty, at the very least for their second playthrough. Whether this should be seen as a positive or a negative will depend on your perspective. As someone who is generally not a tactical genius, I personally enjoyed the power fantasy aspect of crushing the opposition for once, but just be aware that with the current balance (1.2) it is still trivial to break the game over your knee, if you are the munchkin type.
Graphically, as you would expect from an AA developer where that was never the focus anyway, Rogue Trader is just about serviceable. Some of the animations and in-game cutscenes might look amateur if you are used to AAA polish. This does not really bother me as such, but I imagine it can look jarring to others. The exceptions are the generally excellent and presumably hand-drawn character portraits, as well as the illustrations that accompany the CYOA sections.
I honestly do not remember much about the sound design and music, other than that it was neither offensively bad nor incredibly memorable. I suspect that one of the things that keeps the sound from standing out to me is that, by necessity, it had to be appropriate to the generally depressing, industrial 40K environments you traverse, which limits your options.
I would, however, like to commend the excellent English voice acting. Despite the much lower budget at Owlcat's disposal, some of the voice actors in this game are almost comparable to Baldur's Gate 3's main VA cast, which is high praise indeed. They did a great job conveying the zealous nature of many of these 40K archetypes, and usually without hamming it up too much, which is a difficult balance to strike.
Overall, despite notable idiosyncrasies such as the relatively low difficulty and the 40K setting, Rogue Trader is very much an Owlcat game. That means it does anything it possibly can to scare away new players, but if you persevere and get invested in the setting, characters, and mechanics, it will reward you many times over. In fact, I would say the barrier to entry is actually significantly lower than to Wrath of the Righteous, since mechanically it is much more forgiving, and (on the default difficulty) you are allowed to make mistakes all the way up until the end. I can easily recommend this game to any CRPG fan who doesn't mind the 40K setting, or conversely to anyone interested in 40K who doesn't mind CRPGs.