Perhaps on the rotary control it may be okay, as it isn't a very expensive part, but in general I wouldn't use any fasteners on the Rohloff hub that weren't blessed by Herr Rohloff.
Rohloff has an authorised workshop somewhere in the States. I don't know where it is, but read about in an account of a tour across the States. Possibly Crazy Guy on a bike. He sent a Rohloff wheel by courier and huddled in a motel until the courier returned it from them. I imagine they would have small items like the correct length screws readily to hand, or will know who stocks Rohloff bits in the States.