Protagonist
Character Role Analysis
Humankind
As we've noted elsewhere, character is not so important in R.U.R.. It's more a play about ideas. In that vein, the real protagonist here isn't Helena or Domin or any one character, but humanity itself, which is striving for utopia and mastery. So you get to cheer humanity on. Go humanity! Strive! Strive! Str… oh, ouch, watch out for all those angry robots and—oh. Oh dear.
Well, being a protagonist isn't all happy flowers and heroism. Sometimes you trip and fall and exterminate everyone on earth. But get up and keep trying humanity. We believe in you, anyway.