Clearly they are NOT going to operate with a FB. This is going to be a full throttle O with 3 WRs most of the time, 1 back and 1 TE. They are going to continue to spread the field, and run zones right and left and let Gurley pick the hole.
Simply no place for a FB. Why did they take him in the first place? Who knows. They likely didn't really know who they were, what they were able to do, etc. And Gurley didn't exactly have a great year in 2016, so maybe the thinking was that a FB could help him out. Cutting Rogers this early acknowledges that McVay has the guys he needs......and he doesn't need a true FB.