We must address the elephant in the Roxy Theater. is not an official Disney+ release. Disney currently holds the rights, and they have shown little interest in producing a native 4K HDR master from the original negative (likely due to cost and the niche market).
If you want to experience the "Holy Grail" version of The Rocky Horror Picture Show 1975 - 4K Upscaled , follow these general guidelines: The Rocky Horror Picture Show 1975 - 4K Upscaled