The SXSW-premiering Rolling Papers, which opens in theaters today from Alchemy, finds a sharp angle to cover the rise of legal weed in the state of Colorado. Even before recreational marijuana use was legalized in Colorado, The Denver Post launched a department devoted to covering the pot beat, “The Cannabist.” It’s by focusing on editor Ricardo Baca and his team of journalists that producer/director Mitch Dickman tells a story that’s about changing cultural mores, the struggles of print journalism, and getting high in the Mile High State.