Gainer has compared the effects of sodium sulfite on Rodinal with other sodium additives. The info on sodium ascorbate is in this thread:
(there was a url link here which no longer exists)
That thread includes some info on adjusting the times and dilutions when adding 4g/liter of sodium ascorbate to Rodinal, from Gainer's PhotoTechniques article in Jan-Feb 2002, "Salt to Taste?".
He compared adding sodium ascorbate to Rodinal 1+50 with 100g/liter sodium sulfite. I used to use Rodinal 1+100 + 45g/liter sodium sulfite and was pleased with it. Notice that the ratios of sodium sulfite to concentrate are about the same in both uses.
I recently tried Calbe R09 + sodium ascorbate with HP5+, comparing it to P-C-TEA, and liked P-C-TEA better. Both gave a pretty true 400 ISO, and P-C-TEA was about the same in terms of accutance, but with much smoother grain and excellent tonal rendition.
Gainer also recommends trying borax (1g/liter in 1+50 Rodinal) in place of sodium sulfite at:
http://unblinkingeye.com/Articles/Rodinal/rodinal.html
Read down to the bottom of the article. He gives time adjustments for adding borax there as well. I haven't tried this yet myself, so can't comment.
Hope this helps.
Lee