There is no way that Oswald killed Kennedy from the room he was in. Also Oswald wasn't even there, when he was a child he got his tonsils removed and his dead body had tonsils meaning someone pretended to be him. Also Oswald was behind Kennedy and the killing shot came from the front and went through his head.
Ya of course there wasn't, he was dead. No conspiracy theory holds weight. Oswald was a disturbed communist, just the sort of person who would kill a president, much like McKinley's assassin. He had photos of a generals house who he had previously tried to assassinate. He also was a decent marksman in the marines and could have made the shots that killed Kennedy. Also, if someone was shooting from the grassy knoll, they would have been seen by the people on the knoll, or by Abraham Zapruder. I have been to Daley plaza and seen where Abraham stood while he was filming. It is literally right next to the fence where the "shooters" supposedly were. Especially as his camera was moving in that direction so when he looked up he would have seen if anyone was there. Also, photos were taken of the grassy knoll during the assassination and no one is there, though conspiracy theorist have tried to find people in the photo.