My Rolhoff wheels are built with standard Sapim spokes and nipples. [...] I am curious what the story is regarding spoke elbows.
This is about more than just the heads and the elbow "dimensions".
First of all, if your wheel is built with Sapim Strong spokes (you'll know them when you see them -- they have butt-ugly butts), you're okay. The Sapim were designed with Rohloff hubs in mind a whole lotta years and circumnavigations ago.
If your wheel is built with other Sapim spokes, you're still okay. After all, your wheel has served you faithfully through several strenuous tours. The support ring mod was probably gilding the lily too far, but it can't hurt.
Something else to consider before you rebuild those wheels with different spokes: you'll be building in new stresses when there are already different spoke-head impressions in the ali. That strikes me as an unnecessary risk.
The ideal Rohloff spoke, aesthetics aside, is butted, has a particular angle to the bend (and the thickness in the bend is also controlled), and seats the head differently from other applications. Sapim's own Polyax nipples can help with the head seating (by letting the spoke enter the rim at the angle the hub flange requires -- the nipples' trick seating is described by the name, polyaxial). The Polyax nipples are anyway supposed to be used with the Sapim Strong spokes, presumably because you don't want to put uncontrolled stresses on a bunch of spokes that powerful for fear of what else they might bend in unloading themselves.
My everyday bike has a 170kg load rating. I don't suppose I've ever exceeded it but I do sometimes take a solid wood easel with me when there's a wind blowing, probably 50 pounds by itself, and other heavy equipment, and paints are basically earth and rocks in tubes, and I'm no Twiggy, but I've had no cause to use the two Sapim Strong spokes my bike-builder gave me in the "Welcome pack", so I'm a fan of the Sapim Strong despite cringing every time I notice their inelegant proportions.
Check out the link JohnR has posted.
If you're really feeling paranoid, there used to be heavy duty rims made by Exal especially drilled at a special angle for the Rohloff hub. These are the rims I have (without the graphic, of course) but I can't find the description of the drilling of this particular offer:
https://www.starbike.com/en/exal-xl-25-rim-black-28-25-622-vh8.5mm-single-eyelets-36h/