By DAVID BAUDER AP Television Writer NEW YORK Veteran CBS White House correspondent John Roberts, snubbed by his network during the long search for Dan Rather's successor, has jumped to CNN. As a senior national correspondent based in Washington, Roberts will report for various CNN newscasts throughout the day, said Jon Klein, president of CNN/U.S., on Wednesday. He starts on Feb. 20. Roberts, 49, has been CBS News' chief White House correspondent for six years, and anchored the Sunday edition of the "CBS Evening News" for more than 10 years. He was widely considered the top internal choice to succeed...