HP5+ works fine in Rodinal.(posted 8250 days ago)Try Rodinal 1:100 W/ 20G/L sodium sulfite added, 11'30"/68F rotary agitation, EI 320. If you don't have any sodium sulfite, give it EI 200-250. For intermittent agitation add about 15-20% time.
For 1:50 try a couple minutes less time as a starting point.
The added sodium sulfite isn't enough to have any significant effect on graininess; what it does is open up more development sites, giving a little real speed increase with Rodinal.