Supporting southern unity against "freesoil aggression" (Bailey, p. 70), Roberts aligned himself in the 1850s with states' rights Democrats against more nationally minded Texans who identified with Sam Houston. Though not counted among Texas's fire-eaters, he apparently became convinced by 1860 that the election of a Republican president would warrant southern independence. Accordingly, as Abraham Lincoln's victory became apparent, Associate Justice Roberts began to plot strategy with similarly inclined politicians and made a much-publicized speech in Austin supporting secession. Now governor, Houston opposed precipitate action, so Roberts and his allies issued their own unsanctioned call for a secession convention. Gathering in late January 1861, the delegates chose Roberts convention president by acclamation. Roberts appointed a committee on public safety, which arranged for volunteer forces to seize federal property, evict U.S. soldiers from the state, and raise troops. After the electorate endorsed the convention's secession ordinance, the body deposed Houston because the venerable governor refused to swear allegiance to the Confederacy. Roberts had wished secession to be an orderly process and afterward made much of its constitutional justifications, but he never shrank from declaring that its essential object was to perpetuate the enslavement of an "inferior" race. Not a planter himself, neither was Roberts disinterested. He owned eight slaves in 1860.
Patrick G. Williams, "Roberts, Oran Milo," American National Biography Online, February 2000, http://www.anb.org/articles/05/05-00662.html.