Denoise seems 100% necessary for a close to clean final render with Blender. From my experience you can get most of the way in Renderman without denoise being necessary, although obviously it helps. You just don’t NEED it with Renderman - you can often get away with cranking the settings and still have half decent render times(depending on you’re shooting for) without any denoise(although I still usually us it cuz, why not). To turn it on in Blender go to the render layers tab in the properties editor and scroll to the bottom. You’ll find a check box for it here. Check it off to turn it on. Once on, it helps clean up the image for sure, but they’ve still been quite splotchy for me generally. There are various techniques you can use to help minimize the noise like drowning it out with more light(which isn’t always ideal), turning the sun bounces down to 1 or 2, use portals, check your hdri map resolution, clamp indirect at a low value(around .2 to .5), use larger more distant/spread out light sources - none of these techniques have fully cleaned up my renders though. However I just did a test boosting the radius setting on the denoiser to higher values and this has cleaned up the splotchyness drastically, with little effect to render times while maintaining sharpness and texture quality. I finished with it at 22(above the default of 8).