There is plenty of evidence from a variety of different sources to link Oswald to the rifle found on the 6th floor. The rifle used to assassinate JFK. The only person ever associated with that rifle is LHO. Once that is accepted as fact, this becomes a very simple case.
If you had previously tried to assassinate someone with that same rifle, and then it was used to kill a POTUS, you too would probably deny ownership of said rifle during the hub-bub following your suddenly being corralled inside a theater/rendezvous. Oswald certainly was involved in the assassination. He probably built that wall of boxes hiding the sniper's nest from view on the 6th floor. His rifle was stolen from the Paine garage and used during the JFK Assassination while he was calmly sitting inside the lunchroom on the 2nd floor. He's certainly no saint, but he did not fire that Carcano from the sniper's nest on the 6th floor and then hide the rifle that he knew was tied to him on the same floor only feet from the sniper's nest that he constructed. Makes absolutely no sense. None