A teenager is facing charges that he fatally shot a man in Roxbury, authorities said. Andrew Britt, 18, of Dorchester was arrested Tuesday night in the slaying of Shawn Taylor, 28, at 37 Copeland St., in the predawn hours of Dec. 11, Boston police said. A not-guilty plea was entered on his behalf Wednesday in Roxbury District Court to charges of murder and unlawful possession of a firearm. He was ordered held without bail and is scheduled to return to court Feb. 14, prosecutors said.Travis Andersen can be reached at firstname.lastname@example.org. Follow him on Twitter @TAGlobe.