While some bands build an admirable following by busily marketing and selling the image of baby-doll sweetness, Erin Roberts of Porlolo (playing with Rogue Wave and Born in the Flood, Thursday, June 24, at the hi-dive) effortlessly embodies it. The vocalist/guitarist's modest demeanor, complete lack of pretension and stark sincerity are nothing short of mesmerizing. Roberts doesn't fit any modern mold. She brings to mind a Dust-Bowl-era moppet, blown in like a tumbleweed from a bygone era. A rag doll with a naive yet world-weary voice, she fronts an outfit that lays down a firm platform for her earnest exorcisms. After a jaunt with the folk-flavored slo-core of A Dog Paloma, Roberts wisely moved on to take center stage and expand on her former band's sound. She abandoned Paloma's addiction to melancholy in favor of a unit with a more upbeat, straightforward and at times stereotypical approach. But any danger of familiarity is quickly dispersed when Roberts pauses mid-song, ceases to strum her guitar and blows her horn: The haunting yet hopeful wail of a trumpet is startling and unexpected within the usually predictable parameters of rootsy rock. Now that Roberts has stepped out of the shadows, intrigue is never far from her lipsor our ears.