From watching the documentary, and seeing where his man-servant Tommy started using steroids at Gold's gym, and then Rose lying about ever working out at the same Gold's gym (they showed a recorded interview of Rose from the same time where he tells the interviewer he works out there) is about the time Rose had around 3,700 hits, so there is no doubt in my mind that at least his last 500 hits came when he was using performance enhancing drugs, but perhaps even earlier.
Like Bonds, he was a phenomenal hitter without the use of any drugs.