Thank you for proving my point. The RRHOF elects many artists from varying genres of music regardless of their closeness to "rock and roll." edit to add: Few people would consider Ramones or Metallica to be 'rock and roll' instead Punk and Metal respectively.
If James Brown, the godfather of soul, is rock and roll, as you acknowledge, and so much of hip-hop is directly descended from his rhythm sections, then hip-hop is a descendant or derivative if 'rock and roll' as well. You can make the lines to WH from Aretha or Janis or Tina. DM is the commercial viable line of electronic 'rock and roll' that includes Kraftwerk, Suicide, and Joy Division (and Yaz and Erasure).