That's not a rosin paper stain, that's rust. Rosin paper is a darker/reddish brown, this is orange. What most likely happened was the paper was put down before everything was cured, or there was some moisture present somewhere. The rosin paper could have slowed down evaporation and caused it to sit. There are ferrous minerals in this type of marble and they can start to oxidize with moisture, in turn leaving rust stains like this.
If it is from the surface and are just superficial, they can be removed. If it is from within the stone itself, the pieces will need to be replaced.
Buy a gallon of Klenztone #3 from Regent Stone Products. DO NOT DILUTE. Pour a small amount on the surface and let it sit for 10 seconds, then scrub with a soft brush. If the stains are from the top, they will disappear. If anything can get rid of the rust stains, Klenztone can. Do not buy #1, #2 or #4. Buy #3 and DO NOT DILUTE IT. If you dilute it, it turns into hydroflouric acid.
Klenztone #3 will etch granite, glass, metal, porcelain, glazed ceramic and just about everything else EXCEPT marble, limestone and travertine. If you use it straight from the bottle, it won't hurt the marble.
https://www.regentstoneproducts.com/item_detail2.aspx?ItemCode=KLENZTONE
Also, if the staining is nowhere else other than around the toiled area, have the toilet removed and the wax ring inspected or replaced.