Roseanne Arnold has given new meaning to the concept of writing by the numbers.Arnold, star of the high-rated Carsey-Werner Co. sitcom “Roseanne,” issued numbered T-shirts to each of the show’s 19 staff writers during last week’s table reading. Although a few of the writers were said to have been a bit put off by being reduced to a number — particularly in light of the Arnolds’ penchant for high writer turnover on the ABC series — most took the gesture in the spirit in which it was reportedly intended: “to make everyone feel welcome and at home,” said Jay Daniel, one of the exec producers on the series. The roster of writers, including co-exec producer and head writer Rob Ulin, is significantly more crowded than the average comedy series because producers Roseanne and Tom Arnold have sought to augment the show’s staff with stand-up comics and other unestablished writers along with the main cadre of scribes. “Rosey and Tom have encouraged us to use inexperienced writers along with the core of the more experienced staff,” Daniel said. “We found that it just gives you a fresh perspective in the room.” Daniel added that despite the number of writers involved, the cost of maintaining such a large staff isn’t so outlandish as it may sound because many are newcomers who command relatively modest salaries. “Roseanne” has completed production on three episodes of its sixth season; new segs begin airing Sept. 14.