A combination of factors led to the demise of Roseburg Livestock Auction Inc. last month, according to the sale yard's operators.The auction's owner, Larry Cookus of Roseburg, said he "kind of got caught up in my own optimism" when he bought the Wilbur business two years ago.A worse-than-expected season last fall, changing approaches to marketing livestock, increasing mobility of producers and competition from livestock brokers and video sales all contributed to the auction yard's abrupt end on May 18.Plus, Cookus said, animal consignments must be high in order to cover the overhead expense of running an auction facility."There's just not …