scarlson thanks for those tips, especially about filing the hub slot verses removing material from the spoke.
These wheels are filled with multiple challenges:
First, the front wheel is a low-low flange hub for a 18 spoke radial laced rim. I have a spare front wheel, but those spokes are about 12mm too long for the rear wheel, drive side (the side I need two spokes for). Since the spokes are bladed, they can't be shortened to my needed 278mm length.
Second, the rear is a low-high flange hub. The non-drive side is low flange and laced radially with 8 spokes. The drive side is high flange, laced one-cross, with 16 spokes.
Third, the spoke diameter at the round ends is 1.8mm. All modern bladed straight-pull spokes appear to be 2mm at the round ends. I've only been able to find J-bend spokes in the 1.8mm size.
Fourth, as noted before, the hub end has the flattened dome-top end, instead of the more traditional shapped end of most spokes.
Finally (and this is mentioned early on in this thread), the Roval spokes use a unique brass nipple with a nylon spacer between it and the inside of the rim (see picture in post #18 above).
I now realize that the Roval nipples will not work on the 2mm threaded ends of the DT spokes I ordered.
I'm coming to the conclusion that I'll either:
---Give up on the Roval wheels until original replacement spokes or a reasonably priced rear wheel show up on ebay.
------Or bite the bullet and spend $250 to buy the pair currently on ebay.
---------Or just give up!