I think he's been good. A lot of people just expected him to be that guy bombing up the wing whipping in crosses and scoring long shots. And to be fair at one point he was made out to be that guy. Not sure if he ever was, don't watch Bundesbitch enough to know.
He definitely isn't the most dynamic fullback, I bet he'd be more appreciated with a guy like Conti complimenting the team on the right. But like I wrote earlier about him, he's actually pretty good at moving the ball out of pressure and helping the team retain the ball from deep. That helps when the team is being pressed high on the field. A lot of big teams now have fullbacks that are almost more like a centermid than a second winger. You don't only need an attacking fullback that overlaps his winger and whips in great crosses, a lot of them stay deeper or go central and get involved in the build up more.
I'd like to see more end product from RR, I think he has more quality in his delivery that he could show. But he's been solid, not bad by any means. Let's give him the whole season