Rough Country will tell you not to use the spacers. They clearly state to not modify their lift kit in any way to gain more than the designed lift. Except for cranking the tbars which is ok for some reason...
I ran bj spacers on my truck on top of a Superlift kit which is the exact same as a Rough Country (well used to be, they have recently changed the RC kits to make them a little cheaper) and got to the point where I just didn't like them. It's hard on ball joints, TRE's and the idler arm and I got tired of having no confidence in my truck and always having to replace components. Every component change also results in another $60 alignment too. Just last week I removed the spacers and the blocks I had in the back. I like the way the truck sits better already, but I have to do some pounding and trimming now in the front as a have a slight rub with the 36" iroks.
If I were you I'd keep the body lift and ditch the spacers. You should be able to run 35 or 36" tires pretty easily, and any bigger than that you'll end up hating your truck.