Can these rubber rolls be used over vinyl flooring for a gym area, or will it chemically react &/or stain?

You can install our 3/8" Heavy Duty Rubber Rolls over a luxury vinyl floor. The reason that you can install it over a luxury vinyl floor, waterproof, or rigid core floor is due to these products having a wear layer that protects the actual vinyl. If you were to install this over a standard vinyl floor, we would recommend placing a plastic sheet between the vinyl and rubber. This will help to prevent any reaction from happening between the rubber and vinyl.