The moves the Las Vegas Raiders have made this offseason have quickly improved one of the league's bottom-tier rosters. The Raiders used a flurry of moves in free agency to address several roster needs, allowing them to focus on being productive there as well. Darrell Craig Harris, ON SI Rebuilding the Roster One of Las Vegas' main goals this offseason was to revamp its coaching staff and roster as much as possible in one offseason. The Raiders will need multiple offseasons to complete their mission of rebuilding their roster, but this offseason has been a step in the right direction across the board. The Raiders appear determined to turn things around, no matter how long it may take. Las Vegas' front office knows this; fixing the roster at every level will be necessary. As they enter the thick of Raiders general manager John Spytek's second offseason, the progress is undeniable.…