Roberts , 81 , died at his Atlanta home , his lawyer says . Roberts played Adam Roberts , eldest of ` ` Bonanza '' brothers . His fourth wife , Eleanor Criswill , was by his side when he died Sunday , the family said . Roberts was civil rights advocate , marched with Martin Luther King , he says . He 's known to younger viewers as post - M*A*S*H ' ` ` ' '' John McIntyre .
Roberts , 81 , died at his Atlanta home , his lawyer says . Roberts played Adam Roberts , eldest of ` ` Bonanza '' brothers . Roberts was civil rights advocate , marched with Martin Luther King , he says . He 's known to younger viewers as post - M*A*S*H ' ` ` ' '' John McIntyre .